Electron beam type computer output on microfilm printer

ABSTRACT

An electron beam type computer output on microfilm printer employing an electron beam writing apparatus having an evacuated housing closed by a Lenard window fabricated from a differentially etched bulk supporting member through which the electron beam is directed for permitting egress out of the evacuated housing into a higher pressure ambient atmosphere surrounding the housing with a minimum of beam scattering while maintaining the integrity of the evacuated space within the housing. The thin window portion consists of a material different than the bulk supporting member and not susceptible to the etchant employed to form the window in the supporting bulky member and may be formed by chemical reaction with the bulk supporting member from the class of materials consisting of SiSiO2; Al-Al2O3; Ta-TaO; Ti-TiO; Si-SiC; Si-SiN; Al2O3 on Si; and the like. The thin SiO2, Al2O3, TaO, TiO, etc window layer preferably first is formed to a desired thickness on the surface of a bulk supporting member by chemical reaction with the thin elongated window then being etched in the bulk supporting member by an etchant which does not react on the thin window layer. The electron beam type computer output on microfilm printer further includes an electron sensitive microfilm recording medium and transport means supporting the microfilm recording medium immediately adjacent the thin window portion of the electron beam recording apparatus. Printer control circuit means are coupled to the electron beam writing apparatus and the transport means for controlling the operation thereof. A character generator supplied from a buffer memory unit and controlled by the printer control circuit controls deflection and beam blanking of the electron beam recording apparatus. Use of the buffer memory allows the EBeam COM printer to be easily interfaced with any computer system as a standard plug compatible peripheral equipment.

United States Patent [191. Smith 1 June 4, 1974 ELECTRON BEAM TYPECOMPUTER OUTPUT ON MICROFILM PRINTER Donald 0. Smith, Lexington. Mass.

22 Filed: Dec.15,l970

211 App]. No.: 98,259

[75] Inventor:

[52] U.S. Cl 340/l72.5, 340/173 CR [5 I] Int. Cl. l-lOlj 37/22 [58]Field of Search 340/l72.5, 173, 173.2, 340/173 'TP; 95/45 1561References Cited UNITED STATES PATENTS 3.041.930 7/1962 Davidson. Jr.95/45 R X 3.047.871 7/1962 Hider et a1. 95/45 R X 3.121.216 2/1964 Wolfeet a1. 340/173 TP 3.167.747 1/1965 Hughes et a1. 340/173 TP 3.184.7535/1965 Koster 95/45 R X 3.195.112 7/1965 Hughes et a1.... 340/173 TP3.278.683 10/1966 Ashby et a1. 95/45 R X 3.324.457 6/1967 Ogle et a1.340/1725 3.501.235 3/1970 Anton et al 340/173 TP 3.534.338 10/1970Christensen et al. 340/1725 3.540.361 11/1970 Schira 95/45 R 3.710.3521/1973 Smith et a1 340/1732 Primary Examiner-Paul J. Henon AssistantExaminer-Paul R. Woods Attorney, Agent. or Firm-Charles W. Helzer [57]ABSTRACT An electron beam type computer output on microfilm printeremploying an electron beam writing apparatus having an evacuated housingclosed by a Lenard window fabricated from a differentially etched bulksupporting member through which the electron beam is directed forpermitting egress out of the evacuated housing into a higher pressureambient atmosphere surrounding the housing with a minimum of beamscattering while maintaining the integrity of the evacuated space withinthe housing. The thin window portion consists of a material differentthan the bulk supporting member and not susceptible to the etchantemployed to form the window in the supporting bulky member and may beformed by chemical reaction with the bulk supporting member from theclass of materials consisting of Si-SiO AlAl,O;,; Ta-TaO; Ti- TiO',Si-SiC; Si-SiN; A1 0 on Si; and the like. The thin SiO A1 0 TaO, TiO.etc window layer preferably first is formed to a desired thickness onthe surface of a bulk supporting member by chemical re action with thethin elongated window then being etched in the bulk supporting member byan etchant which does not react on the thin window layer. The electronbeam type computer output on microfilm printer further includes anelectron sensitive microfilm recording medium and transport meanssupporting the microfilm recording medium immediately adjacent the thinwindow portion of the electron beam recording apparatus. Printer controlcircuit means are coupled to the electron beam writing apparatus and thetransport means for controlling the operation thereof. A charactergenerator supplied from a buffer memory unit and controlled by theprinter control circuit controls deflection and beam blanking of theelectron beam recording apparatus. Use of the buffer memory allows theE-Beam COM printer to be easily interfaced with any computer system as astandard plug compatible peripheral equipment.

38 Claims, 9 Drawing Figures 49 a FER /Q{ 03mm" a '05 5mm streams F a[ll m svsral was REGISTER m 48 gm cumt t mm cuscx T0 00mm COITROL accent1 EL must I T STATUS m men were PATENTEDJuu 4- m4 3.8151394 SHEET 2 0F 4LENSB DEFLECTOR CHARACTER GENERATOR FLECTOR A CHARACTER POSlTION INVEnron DONALD 0. SMITH ABCDEFGH IJKLMNOP QRSTUVWX YZI23456 7890') [II FIG3A In fld/zs ATTORNEY PATENTEDJUII 4 m4 3.815094 SHEET w 4 FIG. 4B

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t 1 O O O O O O O o 7 0000 0000 2 :3 2 z L 0000 0000 IHVENTOR g DONALD0. SMITH C JOOO 3 8 00 0 amt/es Q} feez ATTORNEY ELECTRON BEAM TYPECOMPUTER OUTPUT ON MICROFILM PRINTER BACKGROUND OF THE INVENTION 1.Field of invention This invention relates to a new and improved electronbeam type of computer output on microfilm printer.

More particularly, the invention relates to a computer output printer ofthe type which records data to be printed-out from a computer system ona microfilm recording medium and which employs an electron beamrecording apparatus having a novel Lenard window which allows theelectron beam to be brought out into ambient atmospheric conditions fordirect recording of electron images on the microfilm without unduescattering of the beam and while maintaining the integrity of theevacuated electron beam source.

2. Prior Art Situation The end product of most computer systemstraditionally has been hard copy print-outs which are usually in humanreadable form. These hard copy print-outs traditionally have beenobtained from impact line printers such as drum printers, chain printersand oscillating bar printers. In all of these devices, the printingtechnique employed involves an on-the-fly" approach in which high printspeeds are achieved by extremely rapid hammer action againstcontinuously moving type elements. The print cycle is the time requiredto load a buffer storage servicing the printer, decode its contents,print one line including hammer action and recoil, and space the paper.In this process, all characters move past the print hammers, thecharacter to be printed is selected by decoding, and a fast actionhammer, controlled by an actuator, presses the paper against the typeslugs at the exact moment the required character is in correct position.The limiting factors on printing speed with impact type printers. tendto be mechanical in nature and are associated with paper handling andpaper motion. Hence, current impact printers approach the upper limit ofthe fastest printing speed of which impact type printers inherently arecapable and this is on the order of 2.000 alphanumeric character linesper minute.

Computer systems generally consist of three basic components: inputdevices for entering data into the system, a processing unit forprocessing the data, and output devices for recording the processresults. The throughput of a computer system is governed by the slowestcomponent. In most computer system applications, the processing unit andthe input device transfer rates are sufficiently fast so that the outputdevice of the system is the limiting factor in the overall system speed.

Output devices can consist of card punches, paper tape punches, magnetictape unit, or line printers. All of these units can accept informationtransmitted from the processing unit and record the information asdirected by the programmed instructions. However, only the line printerhas the capability of rendering the information human readable. Theother type of output devices require separate off line" stations totranscribe the data to human readable form. Such stations are expensiveand perform only a single function; hence, most "off line" stations havebeen replaced by small computing stations comprising buffer storage andperipheral control units. The buffer storage unit is placed between theinput-output devices and the processing unit and data is transferred oncommand from the processing unit to the bufier storage. and then fromthe buffer storage to the printer. The time required for transfer ofdata between the processing unit and the buffer storage is only afraction of the time that otherwise would be required to transfer thedata directly from the processing unit to the printer. Hence. the lineprinter can be directed to record the contents of the buffer storagewhile the processing unit is free to continue with the processing forthe next data manipulatron.

The prime prerequisites for a good printer are a high transfer rate orspeed expressed as lines per minute and print quality. As stated above,impact printers using some kind of mechanically driven type barcurrently are used extensively where human readable print-out isrequired. Because impact printers require mechaincal movement and aretherefore speed limited, non-impact printers which require no mechanicalmovement to achieve print-out have come into wide spread use. Sincespeed is the major consideration as discussed above, non-impact printershave become quite popular.

Non-impact printers usually employ techniques such as photographic,xerograpic and cathode-ray tube methods where the final copy normally isin the form of microfilm or specially treated paper. Where a hard copyis required, the microfilm image normally is transferred to speciallytreated paper. This is a maor disadvantage of known non-impact printersin that the specially treated paper is expensive and often of unknownconsistency. In addition. the known non-impact printers are incapable ofproducing more than one copy of the print-out. However, non-impactprinters offer the potential of extremely high printing speeds atcomparatively low costs. It is this high speed low cost factor that hascaused a recent spin of activity in computeroutput to microfilmprinting.

Recently, computer-output microfilmers (COM) have come into widespreaduse becaue of their high speed low cost factor and due to the fact thatthey convert machine readable data directly to eye-legible informationon microfilm through the medium of an appropriate microfilm reader.These COM printers constitute a new class of peripheral output devicesfor use with computer systems,

The COM printing process can be briefly summarized as follows:

I. The COM printer sends a signal to the central processing unit of thecomputer system when it is ready to print. Alternatively, the COMprinter could be used with a magnetic tape unit to print out resultspreviously recorded on a magnetic tape. However, for the purposes of thepresent discussion, it will be assumed that the COM printer is on lineand printing results supplied thereto directly from the centralprocessing unit of the computer. The information transmitted by theprocessing unit contains instructions interspersed with the dataconcerning procesures for frame advance, retrieval code, formsprojections and the like.

2. The output data to be printed out is fed into a character generatorwhere it is converted into deflection voltages for controlling anelectron beam for a cathode ray tube (CRT), a photo-diode matrix or thelike.

3. The controlled electron beam is used to construct the desiredcharacter on the face of a CRT or directly onto a film.

4. The image if not written directly into the microfilm recordingmedium, is displayed on the fluorescent face of a CRT and photographed.

5. The microfilm subsequently is developed and distributed for copying,printing or viewing in a microfilm reader.

In general, the most interesting aspect of COM has been the revelationto the electronic data processing industry that microfilm can be theheart of a sophisticated information storage and retrieval system thatcan be and is used on day-to-day active records. rather than deadstorage. In addition, COM is the first practical device that can produceoriginal data at a lower price than it could be produced on paper.

The two basic techniques employed by known COM printer systems areoptics and electron beams. Most of the known systems use an electronbeam in a CRT to produce a light image that then is focused on themicrofilm. Currently. there are approximately 24 commercially availableCOM printer systems of this general type. Another known COM printersystem writes directly into the microfilm with an electron beam whileyet another employs fiber optic devices responsive to a photo-diodematrix to achieve recording on the microfilm. At least one of thesedevices operates like a standard plug compatible peripheral equipmentfor use with known computer systems.

In the past, microfilm information sotrage systems were limited by theirincapacity to record information on film at high speed and theirinability to easily restructure, reorganize and update information. COMhas given to microfilm these abilities. However, with respect toexisting COM printer systems, these known systems all have certaindeficiencies in one respect or another. Those systems employing CRTs forconvertmg the data to light images that then are focused on themicrofilm produce poor quality images due to low resolution.insufficient intensity and the like. While one known electron beam COMprinter system which records directly on microfilm with electron images,over comes certain of these problems, because of its nature and designto bring the electron beam directly to the microfilm recording medium,it is difficult and costly to maintain. This is due to the fact that themicrofilm is brought into the electron beam recording space throughseals which also of necessity lowers the evacuation of the space. Thisin turn results in the burning out of cathode sources for the electronbeam because of the poor vacuum in which they operate. Others of thedevices are incapable of producing good quality images because oflimited intensity or limited resolution.

SUMMARY OF THE lNVENTlON It is therefore a primary object of the presentinvention to provide a new and improved electron beam type computeroutput on microfilm printer (hereinafter referred to as an EBCOMprinter) and electron beam recording apparatus having high speedprinting capabilities together with good resolution and high intensityto provide good quality microfilm prints, and which possesses longcathode life for its electron beam source.

Another object of the invention is to provide an EBCOM printer havingthe above characteristics which is adapted for use with a wide varietyof character formation techinques and is usable with a large number ofdifferent microfilm recording mediums both as to composition (i.e., wetsilver. dry silver. etc.) and form (i.e.. tape. card. drum. disk. etc.).

A further object of the invention is the provision of an EBCOM printeremploying a new recording techinque involving the partial recording of acharacter with each individual scan of a recording electron beam whilemechanically moving the microfilm recording medium transversely to thedirection of the scanning electron beam to accomplish raster recordingof characters in a line after a series of repetitive scans.

A still further object of the invention is the provision of an EBCOMprinter as set forth above which in actuality comprises a combinedcontroller-EBCOM printer having a buffer memory that allows it to beeasily interfaced with any known computer system as a standard, plug-incompatible peripheral equipment and having a print-out speed on theorder of 10,000 to 25.000 lines per minute so that it places little orno constraints on the high speed processing capability of a computersystem with which it is used as a printout device.

In practicing the invention, the EBCOM printer system is providedemploying an electron beam apparaus having a source of electronsdisposed within an evacuated housing together with means for directingthe electrons in the form of a beam toward one of the walls of thehousing. A Lenard window fabricated from a differentially etched bulksupporting member is secured to the wall of the evacuated housing andhas an extremely thin window portion through which the electron beam isdirected for permitting egress of the electron beam out of the evacuatedhousing into higher pressure ambient conditions surrounding the housingwith a minimum of beam scattering while maintaining the integrity of theevacuated space within the housing. The thin window portion consists ofa material different than the bulk supporting member and is notsusceptible to the etchant employed to form the window in the supportingbulk member. Preferably, the thin window ortion is formed by chemicalreaction with the bulk supporting member. lt should be noted at thispoint in the description that the terms thin window portion" and window"are considered to be synonymous while the bulk supporting member formsthe window frame. The bulk supporting member and thin window portionmaybe from the class of materials comprising Si-SiO AlAl,O TaTaO,Tl-TiO, Si-SiC, Si-SiN. A1 0 on Si and the like. In a preferredembodiment of the invention, the differentially etched bulk supportingmember is silicon (Si) and the thin window portion is comprised by athin layer of silicon dioxide (SiO previously formed to a desiredthickness on the surface of the bulk supporting silicon member bychemical reaction prior to etching the window therein.

The electron beam apparatus is of the type including deflecting meansfor deflecting the electron beam along at least one axis of movement andthe this window portion comprises an elongated thin slit having its longaxis extending in the direction of deflection of the electron beam. TheEBCOM printer system is further comprised by transport means forsupporting a mic rofilm recording medium immediately adjacent theelongated thin slit window portion and is designed to move the microfilmrecording medium in a direction transverse to the longitudinal axis ofthe elongated thin slit window. A printer control circuit is coupled toand controls the electron beam apparatus and the transport meanstogether with a character generator which also is coupled to theelectron beam apparatus. The arrangement is such that the electron beamis caused to repetitively scan along the longitudinal axis of theelongated thin slit window while the character generator blanks the beamat appropriate points to provide character formatting and spacing. Ifdesired. X-Y deflection of the electron beam can be provided whereby anentire character is written out as the electron beam is scanned acrossthe width of the microfilm recording tape.

In a preferred form of an EBCOM printer constructed in accordance withthe invention, each character recorded on the microfilm tape recordingmedium is comprised of a matrix of horizontal co-extending and verticaltransversely placed dots measured with respect to the longitudinal axisof the elongated tin slit window and with the equivalent of apredetermined number of dot spacings between characters in each line andbetween each line of characters. Placement of a dot in the formation ofa character in a line of characters and the spacing thereof with respectto other dots comprising each character and line of characters iscontrolled by appropriate manipulation of the beam deflection means andthe beam blanking means of the electron beam recording apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and many ofthe attendant advantages of this invention will be appreciated morereadily as the same becomes better understood by reference to thefollowing detailed description, when considered in connection with theaccompanying drawings, wherein like parts in each of the several figuresare identified by the same reference character, and wherein:

FIG. 1 is an overall functional block diagram of a EBC OM printer systemconstructed in accordance with the invention;

FIGS. 1A and 1B are partial cross-sectional views of novel Lenard windowconstructions used with the EBCOM printer system of FIG. 1, andconstructed in accordance with the invention;

FIG. 2 is a schematic functional diagram of one form of electron beamrecording apparatus constructed in accordance with the teachings of thepresent invention and usable in the EB COM printer system of FIG. 1;

FIG. 3 is a functional schematic diagram of still a different form ofE-beam recording apparatus constructed in accordance with the inventionand usable with the EB COM printer system of FIG. 1;

FIG. 3A illustrates a character mask employed in the embodiment of theinvention shown in F IG. 3; and

FIGS. 4A and 4B are functional block diagrams of still a different formof EB COM printer system constructed in accordance with the inventionand providing a novel recording technique employing partial characterrecording during each individual scan of an electron beam writingapparatus employing the novel Lenard window structure of the inventionas depicted in FIG. 4C.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 1. Electron Beam RecordingApparatus FIG. I is a functional block diagram of a new and improved EBCOM printer constructed in accordance with the invention. The heart ofthe EB COM printer is comprised by an electron beam recording apparatus10 contained within an evacuated housing indicated by the dotted lines11 and including an electron beam source comprised by the cathode 12,control grid 13, and anode l4, maintained at suitable potentialssupplied thereto from a power supply 15. Electrons produced by sources12-14 are formed in the shape of a beam indicated by 16, by a suitablefocusing lens arrangement l7, and directed towards a wall of theevacuated housing 11.

The wall of evacuated housing 11 against which the electron beam 16 isdirected has a new and improved Lenard window structure shown generallyat 18 secured thereto. FIG. 1A of the drawings is an enlargedcross-sectional view of the Lenard window structure 18 and illustratesits construction in greater detail. The Lenard window structure isfabricated from a differentially etched bulk supporting member 19, whichmay be formed from one of the class of materials comprising silicon(Si), aluminum (Al), tantalum (Ta) and titanium (Ti). The differentiallyetched bulk supporting member 19, is secured to the wall of theevacuated housing 11 in a vacuum tight manner, and includes a windowarea or opening 21 etched therein over which an extremely thin windowportion 22 extends. The window portion 22 is formed from the class ofmaterials comprising silicon dioxide Si0 aluminum oxide (Al- O Tantalumoxide (TaO), titanium oxide (TiO) silicon nitride (SiN), silicon carbide(SiC) or the like porperly mated to the characteristics of theparticular material used to form the bulk supporting member 19. Theelectron beam 16, is directed against and through the thin windowportion 22, for permitting egress of the electron beam out of theevacuated housing 11 into a higher pressure ambient space surroundingthe housing. Because of the particular nature and construction of thenovel Lenard window structure 18, this is achieved with a minimum ofelectron beam scattering while at the same time maintaining theintegrity of the evacuated space within the housing 11. As a consequenceof this arrangement, the electron beam may be used to directly recordelectron images on a microfilm recording medium shown at 23 withoutsubstantial impairment of the degree of vacuum of the evacuated spacewithin housing 11. This in turn results in greatly extended cathode lifefor the electron beam sources 12-14.

From a consideration of the materials listed in the above description ofthe construction of Lenard window 18, it will be appreciated that thethin window portion 22 consists of a material different than the bulksupporting member 19 which serves as a frame for holding the windowportion 22 and defines the window opening 21 through which the electronbeam passes in order to impinge upon and pass through the thin windowportion 22 without undue scattering or attenuation. A further desirablecharacteristic of the material of the thin window portion 22, is that itcan be previously formed on the thick bulk supporting member 19 to apredetermined thickness preferably through an appropriate chemicalreaction process involving the surface of the bulk supporting member soas to result in a material which is not susceptible to an etchantemployed to fonn the window area 21 in the bulk supporting member 19.For this purpose, it is desirable that the differentially etched bulksupporting member 19 and thin window portion 22, be from the class ofmaterials comprising silicon-silicon dioxide (Si-$02); aluminum-aluminumoxide (AlAl O;,); tantalum-tantalum oxide (Ta-TaO); titanium-titaniumoxide (TiTiO); Si--SiN; Si--SiC; M or Si; or the like. While any ofthese materials may be suitable the preferred construction is for thedifferentially etched bulk supporting member to be comprised of siliconand the thin window portion 22 be comprised of a thin layer of silicondioxide (SiO previously formed to a desired thickness of the surface ofthe bulk supporting silicon member I9 by chemical reaction prior to theetching of the window area 21 in the bulk supporting member 19. For amore detailed description of suitable SiO layer growing techniques andsubsequent selective etching to form thin SiO windows that could beemployed in the manner taught by the instant invention, reference ismade to an article entitled Film Stripping Techniques for Making ThinSilicon Window" by E. Tannenbaum, of the Bell Telephone Laboratories,Inc., appearing in the Journal of Applied Physics Vol 3l, pg. 940 I960)and to an article entitled Gas Permeation Study and lmperfectionDetection of Thermally Grown and Deposited Thin Silicon Dioxide Films"by S. W. Ing, R. E. Morrison and J. E. Sandor of the SemiconductorProducts Department, General Electric Company, Syracuse, N.Y., reportedin the Journal of the Electro Chemical Society, Mar. I962, pg. 221through 226. Still other suitable microcircuit techniques suitable foruse with the present invention are reported in unclassilied Report No.AD6037 l S entitled Integrated Silicon Device Technology, Vol. III PhotoEngraving by J. J. Wortman et al., prepared by the Research TriangleInstitute of Durham, NC, dated January 1964 and available through theDefense Documentation Center of the Defense Supply Agency of the US.Government.

From a consideration of the above-noted references, it will beappreciated that the production of the Lenard window structure 18 can beachieved with well known and established micro-circuit masking andetching techniques employed in the semiconductor industry. It should benoted that only the window area 21, is required to be etched to form thethin window portion 22 of SiO leaving the rest of the wafer as a bulksupporting chamber that can be used as a sturdy mounting or window framefor securing the window to the evacuated housing I I. The thinness ofthe window portion 22 is subject to excellent control during the SiOlayer growing operation by controlling the extent of thermal oxidation,etc so as to produce an SiO layer on the order of l micron or less downto the order of 500 angstrom units in thickness. The etchant used toform the window area 21, which may be hot chlorine, then will not attackthe underlying thin window portion 22 of SiO;. Thus, it will be seenthat control of the thickness of the resulting window portion 22 isseparately performed in one operation and the subsequent etchingoperation need not be the subject of fine control to result in a desiredthickness window layer 22 since the etchant used in forming the windowarea 21 through the bulk supporting member 19, does not attack thewindow portion 22, that is. it is differential in its action. The othermaterials listed above are also known to possess differential etchingcharacteristics and can be employed in a similar manner to form suitableLenard window structures for use in practicing the invention.

Where silicon or other similar semiconductor materials are used as thebulk supporting member 19. it may be desirable to include a thinconducting layer shown as phantom at 19A to keep the Lenard windowstruc' ture at substantial ground or other potential. This isparticularly required if the sides of the bulk supporting memberdefining the thin window area are to be used for blanking part of afan-shaped beam that is deflected along the longitudinal axis of thewindow, and with respect to which the sides of the window intercept andblank part of the beam as will be described more fully hereinafter. Theconductive coating 19A may extend completely over the back or electronsource side of the supporting member 19 including the thin windowportion 22. If desired this conductive layer could be formed of chromiumby vaporization to a thickness on the order of 3,000-l0,000 angstromthick, and could have an even smaller window area shown at 21A etchedtherein by a suitable etchant which does not attack the underlying layerof SiO or other similar material from which the window portion 22 isformed. Alternatively, the conductive layer 19A could be madesufficiently thin so that it does not unduly attenuate or scatter theelectron beam and could cover the entire back surface of the thin windowportion 22.

Another considerable advantage to the Lenard window constructed in theabove described manner from a monocrystaline supporting member such assilicon, is provided by the uniformly straight lines and sloping sidesthat are characteristic of the window aperture or opening 21 and thatare formed during the etching operation due to the planes of themonocrystaline body. As a consequence, extremely fine, straightuniformly shaped window openings can be fabricated in accordance withthis technique which are particularly advantageous for use with electronoptic recording systems of the type herein disclosed.

FIG. 1B is a partial cross-sectional view of an alternative form ofLenard window constructed in accordance with the invention. In FIG. 1Bthe thin window portion 22a is recessed a few microns (on the order ofZ-IO microns) below the surface of the supporting bulk member of silicon19. By constructing the Lenard window in this manner, the thin targetwindow portion 22 can be protected from abrasion and damage from themicrofilm recording medium 23 which is allowed to contact and ride alongthe lower surface of the supporting bulk member 19 in order to minimizethe space between the microfilm 23 and target window portion 22. Infabricating the structure of FIG. 1B, the lower recession is firstintroduced by suitably etching for only a short period of time thebottom surface of the supporting bulk member 19. Thereafter the entirebottom surface is oxidized to form a layer of SiO of about I,()OO5,000angstrom units thick but may be even as low as 500 angstrom units inthickness. A thin layer of long wearing, low friction conductivematerial such as chromium (Cr) then is deposited by evaporation,sputtering, etc over the layer of SiO, to a thickness of about3,000-l0,000 angstrom units thick. The function of this layer 198 is toprovide a good wearing interface between the Lenard window structure andthe recording microfilm tape 23 and also to act as a lubricating or lowfriction surface for engaging the microfilm.

An extremely fine exit opening shown at 218 maybe provided in theprotective layer 198 by etching this layer through to the underlying SiOthin window layer 22 with an etchant that does not attack the SiO;,layer 22. This opening could be made on the order of lmicrons wide, andcan act as a limiting one-dimensional aperture fo the electron beam 16.This very thin exit aperture 218 can be etched in the layer 198 withequal or better precision and with greater ease than if one tried toform the narrow recession in the supporting bulk member of silicon 19with equal precision. The thin slit 21B thus obtained can then act asthe limiting one-dimensional aperture for the electron beam therebyallowing for greater recording resolution. Furthermore, it is not toodifficult to produce an electron beam having a pinched l shape beam andalign the beam so that the center of the pinched l is focussed on thethin window portion 22. ln this manner an extremely fine electron beamspot of comparatively high intensity can be obtained for providing highresolution recordings on the microfilm recording medium 23.

An alternative method for forming the Lenard target window structureshown in FIG. 18 would be first to apply an overlaying film such as 19of chromium completely over the bottom surface of the supporting bulkmember of silicon 19 which previously has been oxidized to a thicknessof the order of two microns. Then a thin recession is etched in theoverlaying layer 198 and through the underlying oxidized layer to exposethe surface of the supporting bulk member of silicon. At this point thestructure is re-oxidized to form a new SiO layer to the desiredthickness for the thin window portion 22. Subsequently, the back orupper side of the bulk supporting member of silicon is differentiallyetched through to the last mentioned SiO, layer and the conductive layer19A then formed in the manner shown. The conductive layer 19A should besufficiently thin so that it does not attenuate or scatter the electronbeam 16. if desired. an opening such as that shown at 21A in FIG. 1Acould be formed in the conductive layer 19A of the structure shown inFIG. ]B.

it is desirable that the thickness of the window portion 22. bemaintained as thin as possible to minimize both beam attenuation due tothe window and scattering effects of the window on the beam.Accordingly, it is desirable that the window portion 22 have a thickness on the order of 500 to 2,000 angstrom units and possibly even lessif the window area 21 can be made sufficiently thin. The transmittanceof SiO is excellent for a thickness even as high as 2.000 angstrom unitsfor a kilovolt electron beam. Of course for a kilovolt beam or somehigher value than [0 kilovolts, the transmittance would be that muchbetter. However a more serious problem exists due to the scattering ofthe beam by the window portion. A rough value estimated from thepublished literature indicates that :1 l0 kilovolt electron beam isscattered on the order of 18 when transmitted through a 2,000 angstromunit thick SiO film. This can be translated into meaning that a beamspot size on the order of 3 to 5 microns impinging on the SiO, Lenardwindow, would be double that size due to scattering at a distance ofabout 1 l microns away from the window. Again, of course, a higherenergy beam such as a 20 kilovolt beam would experience much lessscattering. In either event, however, there is little or no problem tocontrol the spacing between the microfilm recording medium 23 and theSi0 window 22 so as not to exceed 10 to 15 microns. With a spacing onthis order. the transmittance of the electron beam through the airpresents no problem whatsoever since the representative figure obtainedfrom the literature indicates that a 10 kv beam loses about l0 percentof its energy after travelling a distance of 300 microns in air. Toavoid even this kind of a loss, it would be possible to include theportion of the microfilm recording medium 23 on which the electron beamimpinges in a partially evacuated space or enclosure indicated by thedotted lines 25 which can be evacuated by a vacuum pump 26, an d allowthe microfilm recording medium in the form of a tape to be brought intothe space through suitable sealed openings indicated at 27 and 28. Theprovision of the partially evacuated space within housing 25 would alsotend to alleviate somewhat the stresses on the thin SiO Lenard windowportion 22 in comparison to the stresses that would be obtained ifthebeam were brought directly out into ambient atmospheric conditions. Thiswould be particularly advantageous for those applications where it isdesired to have a quite wide target window portion 22. Alternatively,the window structure of FIG. 18 could be employed to minimize spacingbetween film 23 and the target window 22.

With respect to the microfilm recording medium 23, any known microfilmrecording material can be em ployed which is electron sensitive. Forexample. the conventional silver halide photographic film compositionrequiring wet development processes could be employed. A dry silverrecording microfilm employing thermal processing for developmentpurposes is preferred, however, because of the relative simplicity andspeed with which dry silver can be heated and developed. It is alsopossible to use diazo, vesicular and Kalvar R film recording mediums, orfor that matter any other known high resolution recording film which iselectron sensitive. For the purpose of the instant disclosure, it willbe assumed however that a dry silver, diazo or vesicular recording filmis employed using thermal processing. The form of the recordingmicrofilm medium 23 is unimportant and may comprise tape, cards. drums,disk or any other known structural arrangement whereby unexposed areasof the recording medium sequentially may be brought under the electronbeam 16 emanating from the Lenard window portion 22. In the instantdisclosure, the microfilm recording medium 23 is in the form of a tapetransported between a take-up spool 31 and a play-out spool 32, drivenby suitable drive motors and clutch arrangements controlled by a motorcontroller in the conventional manner. It is preferred that the take-upand drive spool have at least two forward speeds, one for recording andthe other for fast advance to a desired area on the tape as well as areverse, although the latter capability is not required. The take-up andplay-out of the mocrofilm tape 23 may be either continuous at a desiredrecording speed related to the number of lines per minute to berecorded, or it may be stepped in nature through the use of suitablestepping motors. However, if the microfilm 23 is to be moved and stoppedbetween each sweep of the electron beam (as described hereinafter),printing speed will probably be reduced by about l,500 lines per minutewhich may be unacceptable depending upon the type of recording techniqueemployed. if such a stepping motor arrangement is used. however, theprinter should be capable of buffering several lines of data to beprinted in order not to place a constraint on the computer systemread-out.

2. Character Genration and Beam Deflection The alphanumeric charactersto be recorded on the mocrofilm tape 23, can be generated in a number ofdifferent ways. There are three commonly employed techniques now beingused in known COM printers. These employ a shaped beam. a dot matrix anda stroke. Other known techniques not so widely used include generationof symbols by a programmed Control of the electron beam deflection, theuse of Lissajous techniques, dot generation, line generation and thetelevision type raster technique. Generation of characters is mostgenerally done by the application of a computer-originated signal to acharacter generator module which decodes the signal and cooperates witha printer controller to control operation of the deflection and blankingcircuit of a CRT. By such arrangements, the electron beam is moved to aproper location and then intensified to cause a visual output to begenerated.

The following list of known character generation techniques is notconsidered to be exhaustive but is merely set forth as explanatory of anumber of known character generation techniques usable with the presentinvention by appropriate design of the printer controller and charactergenerator circuitry.

FIXED STROKE GENERATOR With this technique the electron beam is causedto follow a predetermined path composed of a number of PROGRAMMED STROKEGENERATOR With this technique, each stroke of the electron beam ischaracterized by 7 bits of data. Three bits con trol the X component ofthe stroke, 3 bits control the Y component and one bit controls theblanking. Of the 3 bits for each component, one controls the sign andtwo control the amplitude. Thus. each stroke describes a motion of thebeam. Several strokes are connected to form characters. This method iscapable of generating quite good characters, but at least 16 strokes orll2 bits of space are required in the character generator memory foreach character to be recorded. Hence. the electronic circuitry requiredto implement this technique becomes elaborate and somewhat expensive.

SlMPLE DOT MATRlX In this technique. the electron beam scans a rastereither horizontal or vertical covering an area of the recording mediumwhere a character is to be formed. The character is generated by gatingthe electron beam (i.e. intensifying it at the appropriate points in thematrix where dots are to be formed. A 5 X 7 matrix is the minimumrequired and a 7 X 9 matrix would be preferred for good qualitycharacter recording. Again, as the number of dots is increased, cost andtrace time likewise is increased.

MOVABLE DOT MATRIX This method is similar to the dot matrix but allowsmore freedom in the dot location. In addition to blanking information.position information is supplied for each dot to be recorded. The scanof the electron beam then no longer is a simple raster. The technique ismore expensive but generates quite good quality characters and requireslittle scan time. For dry-process film recording mediums. the use ofthis technique may be advantageous.

MONOSCOPE OR SHAPED BEAM A monoscope is a tube which contains acharacter mask. A coarse deflection system mask deflects the electronbeam to the desired character and a fine deflection system scans thecharacter. By passing the electron beam through the mask having varioussymbols and characters cut into it, the electron beam is shaped" into adesired symbol. The beam is then deflected to a desired position bynormal deflection techniques. The computer requirements for such asystem are simply positional information stored in memory for eachsymbol. Data is the form ofa symbol code and XY position are required. Alimit of 64 symbols requiring a character mask containing 8 X 8 array ofcharacters can be used with each character being identified by a 6 bit 3bits for the X position and 3 bits for the Y position) signal.

3. Printer-Controller Control Circuitry Suitable printer-controllercontrol circuitry for operating the electron beam recording apparatus inaccor' dance with any of the above-listed as well as other knowntechniques, is shown generally in block diagram form to the left of theevacuated housing. The control circuitry is comprised by a printercontrol logic module 41 supplied from a buffer memory 42 which maycomprise a MOS dynamic shift register having a storage capacity on theorder of words with each word comprising 9 bits. The buffer memory 42 issupplied with output data from a computer system central processing unitwhich data is to be printed out by the EBCOM printer. For this purpose.the memory 42 will be supplied an edited line of data plus a few controlcharacters from the computer. The control characters will operatethrough the control logic module 41 to advance the microfilm tape 23through the medium of the film advance control subcircuit 43, projectand print forms through the medium of a form selector and projector 44under the control of a forms projection control subcircuit 45; developthe recorded images on the microfilm tape 23 by a heat source or othersuitable development system 46 under the control of a heat controlsubcircuit 47 together with controlling the performance of othernecessary functions under the central control of the control logicmodule 41. The output from the buffer memory 42 is supplied to thecontrol logic module 41 through a parity checker and control decodesection 48. The output from the buffer memory 42 also is supplied to acharacter generator module 49 that may comprise a MOS read only memoryor core read only memory having a capacity on the order of 10,000 hitssuch as the TMS 2400 integrated read-only memory circuit chipmanufactured and sold by the Texas Instrument Co. The charactergenerator 49 also is under the control of the control logic module 41which serves to clock appropriate character forming signals out of thecharacter generator 49 for supply to the electron beam recordingapparatus 11. Control logic module 41 therefore serves as a centralcontrol employing a relatively simple set of logic elements fordeveloping the necessary clocks and control signals to be used ascommand signals for the various components of the E COM printer systemand also for communicating with the computer system central processingunit to inform it when additional lines of data are to be supplied.detection of errors, etc.

Depending upon the particular character formation techniques employed,the printer-controller control circuitry would be structuredappropriately to implement the desired technique. For the purpose of thepresent disclosure, it will be assumed that the EB COM printer systemshown in FIG. I will record a line of full characters across the widthof the microfilm recording type 23 one line at a time for each scan ofthe electron beam. Hence. it will be necessary that the target windowportion 22 by sufficiently wide to accommodate the height of acharacter. In FIG. 1 it is assumed that the longitudinal dimension oftape 23 extends between the spools 31 and 32 and the width of the tapeextends into the plane of the paper. Accordingly, it will be appreciatedthat as shown in FIG. I, the viewer is looking at a cross sectional viewof the target window portion 22 and that this target window portion willbe in the form of an elongated thin slit extending into the plane of thepaper.

With the electron beam recording apparatus structured in the mannerdescribed in the preceding paragraph. the apparatus would be designed toinclude deflecting means shown generally at for deflecting the electronbeam along at least the longitudinal axis of the elongated thin slittarget window 22. Further. since the target window is sufficiently wideto accommodate the height of a character, additional means shown in FIG.I as comprising a micro deflection system 51 are pro vided fordeflecting the beam 16 along XY axes to cause it to trace out thecharacter patterns to be recorded. This coupled with appropriateblanking (enhancement) of the electron beam by the application ofsuitable control signals to the control grid 13, will result in theformation of electron images on the surfaces of the microfilm recordingtype 23 in accordance with the characters desired to be recorded. Forthis purpose fine X and Y control voltages are supplied to the microdeflection system 51 from a fine X and Y deflection control voltagesubcircuit 52 that in turn is controlled from the character generator49. For certain of the techniques it would be possible to control thefine deflection control circuit 52 directly from the control logicmodule 41 depending of course upon the writing technique employed. Foreither arrangement. the control logic module 41 supplies the requiredslow trace. fast retrace (reset) deflection signals required to causethe electron beam I6 to be scanned back and forth across the entirelength of the elongated thin slit target window portion 22. Thesevoltages are supplied through a course deflection control subcircuit 53to the course deflection means 20 which may comprise electromagneticdeflection coils. I t is of course possible to employ eleectrostaticdeflection plates in place of the electro-magnetic coils illustrated inFIG. 1. Beam blanking (enhancement) control signals are supplied to thecontrol grid I3 of the electron beam recording apparatus from a suitableCRT gate driver control subcircuit 54 that in turn is supplied from thecharacter generator circuit 49. For a more detailed description ofsuitable circuitry for the construction of the CRT gate driver,deflection circuits. stepping motor control. digital-analog conversioncircuitry, buffer memories and the like, reference is made to a numberof issued United States patents and publications relating to theelectron beam recording art such as U.S. Pat. No. 3,195,112 W. C.Hughes. et al.. issued .luly l3. I965; U.S. Pat. No. 3,167,747 W. C.Hughes. et al.. issued Jan. 26. 1965; and U.S. Pat. No. 3.l2l.2l6 J. D.Wolf. et al.. issued Feb. 1 l. 1964. All of these patents includedetailed descriptions of the construction and interconnection of anumber of elemental subcircuits illustrated in block diagram form in thepresent disclosure and readily could be utilized by one skilled in theart to fabricate an EBCOM printer system according to the presentinvention.

FIG. 2 is a schematic. sectional view of an electron beam recordingapparatus suitable for use with the EB COM printer system of FIG. Iwhere it is desired to perform character writing in accordance with themovable dot matrix technique described briefly above. For this purpose,the electron beam recording apparatus 11 shown diagramatically in FIG. 2includes all of the elements listed in connection with the electron beamrecording apparatus ll of FIG. 1. In FIG. 2 however the electron beamrecording apparatus is shown in a different plane so that in effect theviewer is looking at a cross sectional view of the microfilm recordingmedium 23. Thus. it will be appreciated that the view shown in FIG. 2has been rotated substantially with respect to the view shown in FIG. 1.Also in FIG. 2 the construction of the micro-deflection system 51 hasbeen illustrated in greater detail.

The micro-deflection system 51 is comprised by a linear array of 22micro-deflection lenslets which are arranged along the longitudinal axisof the elongated Lenard target window portion 22. The construction ofthe micro-deflection lenslets has been described in detail in a numberof published articles, and hence has not been illustrated inconstructional detail. Briefly. however, the micro-deflection lenslets(sometimes referred to in the art as fly's eye lenslets) are fabricatedfrom a serial array of planar members 51A, 51B. 51C and 51D. Theseplanar members are stacked pancake fashion tranverse to the path of theelectron beam 16 and have appropriate openings or apertures thereinthrough which the electron beam 16 passes. The plate 51A comprises anaperture plate having a potential of about l5 kilo volts applied theretoand through which the electron beam 16 is sequentially scanned by meansof appropriate deflection signals supplied to the course deflection coil20A and 208. In this manner, the electron beam 16 can be causedsequentially to scan across each of the 22 micro deflection lensletswhich in turn extend across the length of the elongated thin targetwindow 22 and the width of the microfilm recording tape 23. The plateSIB also has a potential of about l5 kilo volts supplied to it andserves as an accelerating micro deflection lens for accelerating theelectron beam past the two micro deflecting plates 51C having the finehorizontal or Y deflecting control signals supplied thereto from thecontrol subcircuit 52 in FIG. 1. Within the area of view of eachmicro-deflection lenslet, the electron beam can be deflected along thelongitudinal axis of the elongated thin target window 22 to some 6character sites spaced along the width of the microfilm recording tape23. ln conjunction with the horizontal or fine Y placement of electronbeam 16, the fine vertical or X control potentials are supplied to theplate 51D for deflecting the electron beam vertically (transverse to thelongitudinal axis of the elongated thin window 22) to provide dotplacement in the character formation technique envisioned. Concurrentlywith deflection of the beam in accordance with the character positioncontrolling signals supplied to the respective X and Y micro deflectinglenslets formed on plates 51C and 51D. beam blanking (enhancement) isaccomplished by provision of suitable control signals to the controlgrid 13 from the gate driver control subcircuit 54 in FIG. 1 that inturn is supplied from the character generator circuit 49. It isanticipated that with such a structure the appropriate energizingpotentials would be supplied to the aperture plate 51A and acceleratingplate 518 from the power supply circuit 15 with the cathode 12 beingmaintained at a potential of -20 kilo volts and anode 14 maintained at apotential of about l kilo volts corresponding to the potential of theplates 51A and 518. The conductive film 19A or 19B of the Lenard windowis grounded to prevent build up of charge on this element. This shouldprovide an electron beam having a current density of about 50 amperesper square centimeter formed into a focused beam of about 5 microns spotdiamter by the coarse and fine focussing lens assemblies 17 and 518. Amore detailed description of a suitable electron beam write-readapparatus employing a microdeflection lens assembly and similar to thatshown at (1-1) in FIG. 1, is set forth in US. Pat. No. 3.7l0,352 Smith.et aL, issued Jan. 9, l973, the disclosure of which is herebyincorporated by reference.

In operation it will be appreciated that as the electron beam 16 iscaused to scan say from left to right across the width of the microfilmrecording tape 23 by coarse deflection lens 20A and 2013. it willproceed sequentially along the serially arrayed micro deflectionlenslets 5|. Each individual micro deflection lenslet 51 will in turncause the beam to be deflected horizontally across the width of the tapecorresponding to six character sites. Since there are 22 lenslets thiswill allow 132 characters to be recorded in a line across the width ofthe microfilm recording tape 23. Within each of the micro deflectionlenslets, the X deflection voltage will cause the focused electron beam16 to be deflected in the vertical X (transverse to the longitudinalaxis of elongated thin slit window 22) direction by an amountcorresponding to the height of the characters to be recorded so as toscan or write out in conjunction with appropriate beam blanking(enhancement) the characters to be formed at each of the six charactersites within the field of operation of each lenslet. Upon completion ofa recorded line of characters the transport mechanism causes themicrofilm recorded tape to move a distance corresponding to the spacingof each line of characters during the intervals that the electron beam16 is retraced back to its starting point to initiate a new writingcycle.

FIG. 3 is a diagramatic view of a different form of an electron beamwriting apparatus structured to provide character generation inaccordance with a modified monoscope technique as outlined brieflyabove. With the arrangement shown in H0. 3 an array of four charactergenerator and micro deflection and focusing lens structures 51' arearranged linearly across the width of the microfilm tape 23 in themanner shown. Each of the character generator micro deflectionstructures 5] includes a character mask (shown in FIG. 3A of thedrawings) having an 8X8 array of alphanumeric characters formed therein.Coarse selection of one of the structures 51' is achieved by appropriateenergization of the coarse deflection coils 20A and fine selection ofdesired character within the array of characters formed on the charactermask disposed within the selected structure 51' is achieved throughappropriate energization of fine deflection means comprised by a fine Ydeflection coil 20B and a fine X deflection coil 20C. The structures 51'also include appropriate focusing lens arrangements for focusing theresultant character shaped electron beam and directing it through theassociated character position deflector micro structure 51 arrangedimmediately below the character generator structure 51'. The finedeflectors in micro structure 51' are designed to deflect the electronbeam to anyone of 33 different character site locations along the widthof the microfilm tape 23 within its view in accordance with finehorizontal or Y position control signals supplied thereto. If desired inplace of the character mask arrangement used in conjunction with finedeflection control signals supplied to the deflection coils 20B and 20C,the micro deflection structure 51 could be provided with transverselydisposed X and Y deflection plates. and character generation could beperformed by these deflecting plates under the character generatorcontrol using for example a raster scan with appropriate beam blanking(enhancement) to form a dot matrix. With such an arrangement, characterpositioning of the beam would be done with the last set 51 of deflectionelectrodes each of which would access 33 character positions, The actualnumber of micro deflection structures required with such an arrangmentwould depend upon the ease of manufacturing and spot size re quirements.With a fan shaped beam and at the cost of an extra character generatormemory. it would be possible to generate more than one character atdifferent positions on the line simultaneously, thus achieving a greaterprinting speed. Such modifications would require greater beam currentfrom the cathode however and might impair cathode life. To overcome thisproblem it is feasible to provide an electron beam recording apparatushaving a replaceable cathode. For example the electron source andrelatively inexpensive electrostatic focusing electrodes could befabricated within a removeable envelope or housing including a Lenardwindow and would be arranged to slip within a second housing containingthe more expensive and microdeflection electromagnetic lens assemblies.For a detailed description of comparable electron beam recording devicesemploying character masks, reference is made to US. Pat. No. 3,382,392Corpew, issued May 7, l968 and US. Pat. No. 3.299,4l8 Treseder, issuedJan. l7, 1967.

From the preceding description of FIGS. 1-3 of the drawings, it will beappreciated that the invention makes available a novel EB COM printersystem capable of high speed, high resolution and high intensityprinting on microfilm at ambient pressure. In addition, the printerincludes the ability to print out graphics and forms by reason theinclusion of the buffer memory and the forms projection system. The EBCOM printer comprises a combined printer-controller that can be easilyinterfaced with any known computer system and because of its highprinting speed on the order of between l0,000 lines per minute to 25,000lines per minute it places little or no constraints on the through-putof the computer system. Because of these characteristics, the EB COMprinter can be used as an on-line COM printer device operable as astandard plug-in compatible peripheral equipment for use with computersystems. It makes available a new and improved electron beam apparatushaving a Lenard window fabricated from a differentially etched bulksupporting member of silicon and silicon dioxide or the like with theLenard window portion having a thickness on the order of 5005,000angstrom units thick. If desired the electron beam apparatus can includeboth electrostatic and electromagnetic deflection lens structure with aremovable electron source whereby the source can be replaced after anumber of hours of use without requiring the complete electron beamrecording apparatus be replaced or rebuilt. By appropriate fabricationof the Lenard window, the size of the window can be used for blankingthe electron beam by the use of appropriate beam blanking deflectionpotentials provided to the deflection lens of the structure. Themicrofilm recording medium used with the EB COM printer may comprise wetsilver requiring a wet developing process. dry silver, diazo, vesicularcalvar or some other dry recording medium and/or technique using thermalprocessing for development. The recording medium may be in the form of atape, card. drum, disk, or any other form presently known in the art fortransporting the recording medium past the Lenard window portion of theelectron beam recording apparatus.

4. High Speed Multiple Scan/Character EB COM Printer System FIG. 4A and48 comprise a functional block diagram of a new and improved high speedmultiple scan per character EB COM printer system made available by theinvention. This system differs from the previously described EB COMsystems in that it employs a very fine elongated thin slit SiO Lenardwindow along which the electron beam is traced repetitively for apredetermined number of scans. Each individual scan of the electron beamis used in conjunction with suitable beam blanking (enhancement) andresults in the recording of a partial character at each character sitealong a line of characters. Concurrently with the microfilm tape widescanning and partial character recording. the microfilm tape is movedtransversely to the longitudinal axis of the elongated thin slit windowso that repetitive scanning of the electron beam for a predeterminednumber of scans results in the raster recording of a line of completecharacters across the width of the tape. For recording in this manner, acontinuous speed tape drive is desired whose speed of movement isrelated to the scanning frequency of the electron beam as will bedescribed more fully hereinafter.

In the embodiment of the invention shown in FIG. 4B the electron beamrecording apparatus is somewhat different in construction from thatemployed in previously described embodiments. The electron beamrecording apparatus 10 shown in FIG. 4B is comprised by an evacuatedhousing ll having an electron source shown generally at l2l 4 includinga cathode, control grid and anode which are not shown individually. Theelectron source 12-14 is mounted at one end of the evacuated housing IIand a Lenard target window shown at 18 is mounted at the other forpermitting egress of the electron beam 16 out of the evacuated housing11 and onto the recording microfilm tape 23. The lenard target window I8is fabricated in the manner previously described in connection with FIG.1A of the drawing and hence will not again be described in detail. Thereis one difference however. in the construction of the Lenard targetwindow which is important to note. Because of the capability of formingvery fine straight cuts or openings defining the target window usingwell known micro circuit etching techniques on a crystallinesemiconductor body such as silicons the target window 18 employed in theelectron beam apparatus in FIG. 4 is made to be a very fine thin slitwhose width is on the order of the diameter of the electron beam I6produced by the electron beam recording apparatus. This slit may be assmall as 5 microns in width and conceivably could extend to as much as aten or 50 micron wide slit or larger, but preferably is as small aspossible to provide good resolution. The length of the target window isof course determined by the length of line of characters to be recordedand should be sufficiently long to accommodate a scanning trace of theelectron beam sufficiently wide to record 132 alphanumeric characters ina line.

Similar to FIG. 1, FIG. 4 illustrates the electron beam apparatusarranged in a manner such that its electron beam is scanned back andforth along an axis extending into the plane of the paper. The microfilmtape take up and play out spools are arranged to transport the microfilmtape 23 in a direction transverse to the longitudinal axis of theelongated thin slit window 18. The electrons produced by the source12-14 are accelerated through an apertured anode plate 61 and directedthrough a spray aperture plate 62 mounted on one end of a four foldelectrostatic deflector element 63. The spray aperture 62 operates as abeam defining aperture to limit the beam current and also serves toshape the electrons in the form of a pencil-like beam. The four foldelectrostatic deflecting plates 63 then operate to deflect or displacethe beam so as to align it along a central axis extending between thesource I2l4 and the Lenard target window 18. The beam of electrons thenis directed through an electrostatic focusing lens arrangement I7 andthrough a second beam defining aperture 64 which may be adjustable ifdesired, and thence through a second focusing lens structure 65. Thefirst focusing lens 17, the second aperture 64 and the second focusinglens 65, which may be either electro magnetic or electrostatic innature, are included in the electron beam recording apparatus to providefurther shaping of the electron beam so as to result in an extremelyfine pencil-like electron beam writing probe having a diameter on theorder of 5 microns. This finely shaped electron beam then travelsthrough an electromagnetic deflecting lens 66 for deflecting theelectron beam across the longitudinal axis of the elongated thin slitLenard target window 18 in the manner described above.

FIG. 4C of the drawings is a diagrammatic sketch illustrating how themultiple scan characters are built up or recorded on the surface of themicrofilm tape 23 as a result of the partial character recordingachieved during each individual scan of the electron writing probeaccompanied by appropriate beam blanking (enhancement). In FIG. 4C thearrows associated with the numerals l and 7 extend in the direction ofthe longitudi nal axis of the microfilm recording tape (and hence in thedirection of movement thereof) and the arrows associated with thenumerals and 8 extend in a direction across the width of microfilm tape23. Each line of characters to be recorded is transmitted in the form ofpulsed, coded, digital electric signals to a character generator to bedescribed herein after which converts the signals to appropriate beamblanking (enhancement) signals that are supplied to the control grid ofthe electron beam recording apparatus 11. Placement of a dot at aparticular point along the width of the microfilm recording tape 23 willof course be determined by this signal in conjunction with thedeflection potentials supplied to the deflecting lens arrangement 66. Asillustrated in FIG. 4C a line of characters is printed by splitting eachcharacter in the line into a matrix of 5 X 7 dots with the equivalent ofa three dot spacing being interposed between each character in a lineand the equivalent of three dot spacing being interposed between eachline of characters in a frame. It is presumed that the now generallyaccepted format of 66 lines in a frame and 132 characters per line isused in carrying out the recording process. The technique is in no wayrestricted to this specific format however and it is cited only asexemplary of one mode in which the novel EB COM system of FIG. 4 can beoperated. From a consideration of HG. 4C it will be appreciated thereforthat some ten horizontal scans of the electron beam is required in orderto complete the recording of a complete line of characters includingappropriate line spacing and seven of these scans will be productive inproducing the character to be recorded in a particular character sitealong the width of the microfilm tape 23. Similarly, only fivevertically placed dots are required to construct the character for eachhorizontally placed character site along the axis of scan of theelectron beam. Which dots in the five by seven dot matrix are blankedand which are enhanced to result in the production of a dot recording onthe surface of the microfilm tape 23, is determined by the charactercontrol signal supplied to the control grid of source 12-14.Accordingly. at any given point along the microfilm tape 23 the electronbeam 16 will be scanned across its width and appropriately blanked orenhanced to produce a partial character dot pattern which whenaccumulated over a predetermined number of l0 scans measured from theinitiation of a new line of characters recording cycle. results in arecording such as the BB shown in FIG. 4C.

Suitable control circuitry for controlling operation of the electronbeam writing apparatus in the above briefly described manner isillustrated in FIG. 4A. This control circuitry is comprised basically bya printercontroller 41. a character generator 49 and buffer memory means42. The heart of the printer-controller 41 is comprised by a dot clockand control circuit 71 that sets up the timing sequence with which theelectron beam will be blanked. The output from the dot clock and controlcircuit 71 is supplied to a modulo-8 horizontal dotposition-in-a-character counter 72 which determines which dots in acharacter extending in the horizontal (co-extending with thelongitudinal axis of elongated thin slit target window 18) direction areto be printed. Modulo-eight dot counter 72 supplies its output over aconductor 73 to the input to a modulo- 132 horizontalcharacters-in-a-line counter 74 whose output in turn controls a rampgenerator supplying a horizontal coil driver amplifier 76 that in turnsupplies deflection potentials to the deflecting lens arrangement 66.The ramp generator 75 develops a substantially linear saw toothwave-shaped excitation potential that is amplified in the horizontalcoil driver amplifier 76 and serves to deflect the finely focusedelectron beam probe width-wise across the microfilm recording tape 23 ina continuous linear manner. At the end of a line of 132 charactersrepresented by 8 X 132 dot clock pulses from the dot clock and controlcircuit 71, the ramp generator 75 produces a retrace potential thatcauses the electron beam deflecting lens 66 quickly to retrace the beamback to its initial starting point while being blanked by an appropriatepotential supplied to its control grid. During this retrace portion.intermediate each line scan of the recording electron beam, a retrace.inhibit potential is supplied back over a conductor 77 to inhibitoperation of the dot clock and control circuit 71. This retrace inhibitpotential is supplied from the output of the modulo 132characters-ina-line counter 74 whose output is also supplied to a modulo66 lines-in-a-frame counter 78 whose output in turn is supplied over aconductor 79 to control the operation of a page and film advance anddevelop control circuit 8] controlling operation of the take up and payout spools 31 and 32 through a motor driver control circuit 82. The pageand film advance and develop control 81 also controls operation of aheat source 83 which serves to develop the electron image written on themicrofilm tape 23 during earlier writing cycles.

The dot clock and control circuit 71 is in turn controlled from theoutput of a buffer control circuit 85 contained within the buffer memorymeans 42 and which further controls operation of a three line buffermemory 86. Additionally. the buffer control 85 communicates via line 87with the central processing unit 88 of a computer system with which theEB COM printer is used as a print out device. The computer systemnormally will include a working memory such as the core memory 89 underthe control of the central processing unit. The central processing unit88 on request from the buffer control 85 will operate to transfer fromthe core memory 89 one page or frame of 66 lines of character into adisc memory unit 91 comprising a part of the overall EB COM printersystem memory 42 which further includes the three line buffer memoryunit 86. The buffer control on direction from the central processingunit indicating that the disc memory 91 is full will initiate read outof the disc memory 91 three lines at a time into the three line buffermemory 86. The three line buffer memory 86 may comprise a conventionalMOS dynamic counter using integrated circuit multi vibrator units, or itmay comprise a memory tube such as the Lithicon or other similar smallmemory means Similarly, the disc memory 91 could be replaced with asmall ferrite core memory, a MOS dynamic counter memory. a Lithiconmemory. or the like. The disc memory 91 serves as an interface betweenthe three line buffer memory 86 of the EB COM printer system and thecentral processing unit of the computer system with which the EB COMprinter system is being used.

The three line buffer memory 86 stores three lines of characters andtransmits them serially one line at a time over conductor 92 to a MOSread only memory 93 that comprises a part of a character generator 49and may comprise a TMS 2400 integrated read-only memory circuit chipmanufactured and sold by Texas Instruments Co. Read out of each line ofcharacters stored in the buffer 86 into the read only memory 93 is underthe control of buffer control 85. In order to inform the buffer control85 of the completion of one scanning line by the electron recordingbeam, the output of the modulo I32 characters-in-a-line counter 74 issupplied over conductor 94 and 95 to a control input of the buffercontrol 85. The output characters-in-a-line counter 74 also is suppliedto the input of a modulo l vertical dot position-in-a character counter96 that supplies its output over line 97 to the read only memory 93. Theoutput from the vertical dot position-in-a char acter counter 96 inconjunction with the character indicating signals supplied from buffer96 and the horizontal in-a-character count signal supplied from counter72 over a conductor 98 to a digital multiplexer 99 connected to theoutput of read only memory unit 93, operates to establish which dot inany given character matrix corresponding to a desired character siteacross the width of the microfilm tape is to be intensified, and hencerecorded on the microfilm tape. The resultant is an intensifying controlsignal supplied at the output of the five position digital electronicmultiplexer switch 99, and is supplied through a grid driver l0] to thecontrol grid of the electron beam controlling apparatus 10. For a moredetailed description of suitable component subcircuits usable in theabove-described EBCOM printer system, reference is made to theabove-cited U.S. Pat. Nos. 3,l95,l l2; 3,l67,747; 3,l 2l,2l6; and tosuch text books as The Source Book of Electronic Circuits published bythe McGraw-Hill Co., John Markus, Ed., Copyrighted 1968, Library ofCongress Catalog Card Number 67-l5037. Any of the known subcircuitsdescribed in these prior art reference texts and patents, or theirintegrated circuit counterparts, readily could be employed by oneskilled in the art to fabricate the above-briefly-described EBCOMprinter system in the light of the present disclosure.

Having described the construction of the multiple scan/character EB COMprinter system shown in FIGS. 4A and 48, its operation is as follows.Information to be printed which is being transferred out of the corememory 89, or alternatively is being generated by the central processingunit 88, is transferred to the disc memory 91 and stored. The discmemory is capable of storing at least one complete page or frame of 66lines of characters with each line containing a maximum of I32characters. When a full page or frame has been generated and stored indisc memory 91, the central processing unit signals the buffer control85 that it is ready to print. Upon sensing that the three line buffermemory unit 86 is full. the buffer control 85 initiates operation of thedot clock and control circuit 71 and printing commences. Upon one linein buffer memory 86 becoming empty the buffer control signals thecentral processing unit 88 to transfer another line of data which itwill do at the next available moment before the disc memory has beenemptied. Thus it will be seen that the printing operation is performedon a line of characters" basis.

Upon the dot clock and control circuit 71 being turned on by buffercontrol 85, a line of characters to be printed is transmitted to readonly memory 93 out of the buffer memory 86 through line 92. Concurrentlyturn on of the dot clock and control will initiate operation of the rampgenerator which will start to sweep the electron beam horizontallyacross the width of the microfilm tape 23. As the electron beam scansacross the width of the microfilm tape in a line, the read only memory93 in conjunction with the digital multiplexer 99 which is under thecontrol of modulo 8 horizontal position-in-a-character dot counter, andthe modulo-l0 vertical dot position-in-a-character counter 96.determines which dots are to be intensified and hence recorded on themicrofilm tape 23. As stated previously the line of characters areprinted by splitting each character in a line into a matrix of five byseven dots with the equivalent of three dot spacing between charactersand between each line of characters. To complete a line of characters,l0 scans of the electron beam across the width of tape 23 is requiredwith only selected ones of a five by seven dot matrix within the 132character positions contained within a line of characters beinggenerated to form the desired character on a given character recordingsite. During this process the modulo-8 horizontal dotposition-in-a-character counter 72 keeps track of the horizontalposition of the beam in any given charcter site along the line ofcharacters being recorded while the modulo 10 vertical dotposition-in-a-character counter keeps track of the particular scan linebeing scanned of the ten scan lines required to form a line ofcharacters. As the electron beam is being scanned across the full widthof the microfilm tape 23, the modulo 132 character-in-a-line counter 74keeps track of which particular character is being partially printedduring any particular portion of a scan of the electron beam.

Once the printing of a line of characters is completed, this fact willbe signaled to the buffer control by the characters in a line counter 74which will then operate to read into the read only memory 93 anotherline of characters to be printed out. Concurrently the centralprocessing unit 88 will be signaled that the printer system is ready toreceive another line of data to be printed. This process is repeateduntil a complete page or frame of 66 lines of characters is printed. Thenumber of character lines printed in a frame is controlled by modulo 66character lines counter 78 which signals the page and film advance anddevelop control circuitry 88 when a frame is completed. It should benoted that while the instant system is described as includingsubstantially simultaneous development of the recorded electron imagefollowing printing of the image in the above described manner, it isentirely feasible for the electron image to be stored on the micro filmand developed subsequently at a more convenient time and under lessstrenuous conditions. Additionally, while in the system of FIG. 4, beamblanking (enhancement) is employed to achieve dot recording, it isentirely feasible to include an additional deflecting signal fordeflecting the recording electron beam probe to one side of the other ofthe Lenard window so as to achieve beam blanking by interception of thebeam by the sides of the Lenard window structures as described earlierwith respect to FIG. 1A of the drawings.

With the multiple scan per character EB COM printer system shown inFIGS. 4A and 4B and employing an electron beam spot size of 5 microndiameter, it would be possible to write characters in theaboveidentified fashion having a height of 75 microns, a width of 50microns and with a spacing of 30 microns between characters and betweencharacter lines. With such a system employing 10 scans per character towrite a character. a complete line of characters could be traced out in24,000 microseconds corresponding to 240 microseconds for a one linescan of l32 partial characters or an average of l8 microseconds percharacter. With a system having the above constraints, the frequency ofwriting each character would be flcharacter l/l.8 X l 550 kilohertz andthe frequency per line would f/line of characters V2.40 X l0 4kilohertz. At these writing rates, the microfilm tape take-up andpay-out spools can be driven by continuous drive motors whose speed ofadvance during a recording operation would be correlated to the inhibitperiod provided at the end of each line scan of the recording electronbeam so that the tape advances a distance on the order of 10 micronsduring this interval before again initiating a write cycle on the partof the dot clock and control circuit 71. it should be noted however thatthe systems specifications listed above are only exemplary and can bevaried widely to meet the needs of any particular installation. Forexample the recording beam spot diameter can be varied from the 5microns indicated up to a 75 micron diameter spot to provide a requiredamount of energy to accomplish high speed recordings having goodresolution and high intensity. Other variation and modifications to meetthe requirements of different high speed printer installations will besuggested to those skilled in the art.

From the foregoing description, it will be appreciated that theinvention provides a new and improved EB COM printer system and electronbeam recording apparatus therefor having high speed printingcapabilities together with good resolution and high intensity to providegood quality microfilm prints. The electron beam recording apparatuspossesses long cathode life for its electron beam source due to thenovel construction of a Lenard window structure. The EB COM printersystem can be adapted for use with a wide variety of character formationtechniques using a large number of microfilm recording mediums havingdifferent compositions such as wet silver. dry silver. diazo, Kalvar,etc and having widely different forms such as tape, card, drum, disc,etc. The invention also makes available to the art a novel recordingtechnique employing partial electron beam recording with each individualscan of the recording electron beam while moving the record mediumtransversely to the direction of scan of the electron beam to accomplishraster recording of characters in a line over a predetermined number ofscans. The EB COM printer system incorporating the above characteristicsactually comprises a combined controller-EB COM printer having a buffermemory that allows it to be easily interfaced with any known computersystem as a standard. plug compatible peripheral equipment havingprint-out speeds on the order of 10,000 to 25,000 lines per minute andeven higher so that it places little or no constraints on the high speedprocessing capabilities of the computer system with which it is used.

While the electron beam recording apparatus described herein has beendisclosed as primarily intended for use in an EB COM printer system, itis believed obvious to those skilled in the art that the novel electronbeam apparatus can find application in a wide variety of uses wherein itis desired to impart the energy of an electron beam to a mediumexteriorily of an evacuated space. Such applications as electron beamanalog recording on microfilm and television picture recording arebelieved to be logical uses for the new and improved electron beamapparatus made available by this invention. Accordingly it will be seenthat the novel electron beam apparatus can be used in a wide variety ofapplications in addition to those detailed above.

Having described several embodiments of a new and improved electron beamtype computer output on microfilm printer and electron beam apparatustherefor. constructed in accordance with the invention, it is believedobvious that other modifications and variations of the invention arepossible in the light of the above teachings. It is therefor to beunderstood that changes may be made in the particular embodiments of theinvention described which are within the full intended scope of theinvention as defined by the appended claims.

What is claimed is:

l. in an electron beam apparatus of the type including a source ofelectrons disposed within an evacuated housing and means for directingthe electrons in the form of a beam toward one of the walls of thehousing, the improvement comprising a Lenard window fabricated from adifferentially etched bulk supporting member secured to the wall of theevacuated housing and having an extremely thin window portion throughwhich the electron beam is directed for permitting egress of theelectron beam of the evacuated housing into a higher pressure spacesurrounding the housing with a minimum of beam scattering whilemaintaining the integrity of the evacuated space within the housing,said thin window portion consisting of a material different than thebulk supporting member and not susceptible to be etchant employed toform the window in the supporting bulk member.

2. thin electron beam apparatus according to claim 1, wherein the thinkwindow portion is formed by chemical reaction with the bulk supportingmember and the differentially etched bulk supporting member and thinwindow portion are from the class of materials consisting essentially ofsilicon silicon dioxide (Si- SiO2); aluminum-aluminum oxide (AL-A1 03);tan talum-tantalum oxide (Ta-TaO); titanium-titanium oxide (Ti-TiO);silicon-silicon nitride (Si-SiN); silicon-silicon carbide (Si-SiC)silicon-aluminum oxide (SF-M 0 3. An electron beam apparatus accordingto claim I, wherein the differentially etched bulk supporting member hasa thin conductive layer formed over at least a part of the surface ofbulk supporting member exposed to the electron beam and extending overat least part of the thin window portion whereby build-up of asubstantial charge on the window can be minimized.

4. An electron beam apparatus according to claim 1, wherein the electronbeam apparatus is of the type including deflecting means for deflectingthe electron beam along at least one axis of movement and said windowportion comprises an elongated thin slit having its long axis extendingin the direction of deflection of the electron beam.

5 An electron beam apparatus according to claim 1, wherein said windowportion comprises an elongated thin slit having a width which is morenarrow than the largest dimension of the cross section of an elongatedelectron beam produced by the electron beam apparatus.

6. An electron beam apparatus to claim 1, wherein the differentiallyetched bulk supporting member is silicon and the thin window portion iscomprised by a thin layer of silicon dioxide previously formed to adesired thickness on the surface of the bulk supporting silicon memberby controlled chemical reaction prior to etching the window therein andwherein the thin slit window portion as a width on the order of -75microns and a thickness on the order of SOD-2,000 angstrom units.

7. An electron beam apparatus according to claim 4, wherein the electronbeam apparatus further includes additional micro deflecting means fordeflecting the electron beam along two transverse axes of movement withrespect to a character wide thin slit window portion for writing a lineof alphanumeric characters, and beam blanking means for blanking theelectron beam at appropriate points along the line of characters toprovide for separation and formatting of the written characters.

8. An electron beam apparatus according to claim 4, wherein an array ofcharacters masks having openings there in forming alphanumericcharacters are arranged along the longitudinal dimension of theelongated thin slit window portion and the deflecting means serves todeflect the electron beam to a selected character on one of thecharacter masks, and the electron beam apparatus further includes microdeflection means disposed intermediate the array of character masks andthe first mentioned deflecting means for focusing and deflecting adesired alphanumeric character-shaped electron beam produced by passageof the electron beam through a selected character opening on one of thecharacter masks to cause the same to be directed through the thin windowportion and a desired point along its length.

9. An electron beam apparatus according to claim 4, wherein an extremelyfine slit window portion is provided having a width on the order of thediameter of the electron beam whereby partial character recording can beachieved during each scan of the electron beam across the longitudinaldirection of the window portion accompanied with appropriate beamblanking at selected points along the path of travel thereof to providecharacter spacing and formatting and repetitive scans of the electronbeam are required for complete character recording.

10. An electron beam apparatus according to claim 9, wherein thedifferentially etched bulk supporting member is silicon and the thinwindow portion is comprised by a thin layer of silicon dioxidepreviously formed on the surface of the bulk supporting silicon memberprior to etching the window therein and the elongated thin slit windowportion has a longitudinal dimension on the order of the length of aline of recorded characters and a thin width portion on the order of 5microns with the thickness of the window portion being on the order ofSOD-2,000 angstrom units.

11. An electron beam apparatus according to claim 9, further includingmeans for blanking the beam of electrons at appropriate points along thepath of travel thereof during the scanning of the beam in thelongitudinal direction of the thin slit window portion.

12. An electron beam apparatus according to claim 11, wherein saidelectron beam blanking means comprises means for producing suitableon-off blanking signals supplied to the control grid of the electronbeam apparatus.

13. An electron beam apparatus according to claim ll, wherein saidelectron beam blanking means comprises deflecting means for deflectingthe electron beam transversely to the longitudinal axis of the elongatedthin slit window portion so that the sides of the supporting bulk memberintercept and blank the beam at points where beam blanking is desired.

14. An electron beam COM printer system including an electron beamapparatus of the type set forth in claim 1, an electron sensitivemicrofilm recording medium, transport means for supporting the microfilmrecording medium immediately adjacent the thin window portion of theelectron beam recording apparatus for recording data thereon, printercontrol circuit means coupled to said electron beam writing apparatusand the transport means for controlling the operation thereof, andcharacter generator circuit means controlled by the printer controlcircuit means and coupled to the electron beam writing apparatus forcontrolling the operation thereof in conjunction with the printercontrol circuit means, said printer control circuit means and saidcharacter generator circuit means being controlled from the output of acomputer system with which the COM printer is used as a print-outdevice.

15. An electron beam COM printer system according to claim 14, furtherincluding buffer memory means intercoupled with the printer controlcircuit means and the character generator means for receiving apredetermined number of lines of data to be printed from a computersystem central processing unit plus control data for directing operationof the printer control circuit means, said buffer memory means servingto store temporarily the predetermined number of lines of data whileeach line of data is being printed out by the COM printer therebyfreeing the computer system central processing unit for furtheroperations during printing of the stored lines of data.

16. An electron beam COM printer system according to claim 15, whereinthe electron beam recording apparatus is of the type includingdeflecting means for deflecting the electron beam along at least oneaxis of movement and the window portion comprises an elongated thin slithaving its long axis extending in the direction of deflection of theelectron beam, said transport means operates to move the microfilmrecording medium in a direction transverse to the longitudinal axis ofthe elongated thin slit window whereby successive lines of data can berecorded raster fashion, said printer control circuit means is coupledto and controls operation of the deflecting means to cause tracing ofthe electron beam along the longitudinal dimension of the elongated thinslit window portion, and the character generator circuit means controlsbeam blanking and character formatting.

17. An electron beam COM printer system according to claim 16, whereinthe differentially etched bulk supporting member is silicon and the thinwindow portion is comprised by a thin layer of silicon dioxidepreviously formed on the surface of the bulk supporting silicon memberby chemical reaction prior to etching the window therein and wherein thethin slit window portion has a length on the order of one line ofrecorded alphanumeric characters on microfilm, a width on the order of75 microns and a thickness on the order of l,000-5.000 angstrom units.

18. An electron beam COM printer system according to claim 17, furtherincluding means enclosing the Lenard window portion of the electron beamapparatus and the microfilm disposed immediately adjacent the Lenardwindow portion in an enclosed space maintained at a reduced pressurerelative to the surrounding ambient atmosphere.

19. An electron beam COM printer system according to claim 16, whereinsaid window portion comprises an elongated thin slit having its longestdimension approximating the length of a line of microfilm recorded alphanumeric characters and having the thin dimension thereof approximatingthe height of an individual alphanumeric character recorded onmicrofilm, and wherein the electron beam recording apparatus furtherincludes additional micro deflecting means for deflecting the electronbeam along two transverse axes of movement with respect to the characterwide elongated thin slit window portion for writing a line ofalphanumeric characters, and beam blanking means for blanking theelectron beam at appropriate points along the line of characters toprovide for separation and formatting of the written line of characters,said character generator circuit means controlling operation of bothsaid additional micro deflecting means and said beam blanking means.

20. An electron beam COM printer system according to claim 19, whereinthe differentially etched bulk supporting member is silicon and the thinwindow portion is comprised by a thin layer of silicon dioxidepreviously formed on the surface of the bulk supporting member bychemical reaction prior to etching the window therein and wherein thethin slit window portion has a width on the order of 75 microns and athickness on the order of LOGO-5,000 angstom units.

21. An electron beam COM printer system according to claim 16, whereinan array of character masks having openings therein forming alphanumericcharacters are arranged along the longitudinal axis of the elongatedthin slit window portion and the deflecting means serves to deflect theelectron beam to a selected character on one of the character masks, andsaid electron beam recording apparatus further including microdeflection means disposed intermediate the array of character masks andthe first mentioned deflecting means for focusing and deflecting adesired alphanumeric character-shaped electron beam produced by passageof the electron beam through a selected character opening on one of thecharacter masks to cause the same to be directed through the thin windowportion at a desired point along its length and thereby record anelectron image of the selected character at a desired point on themicrofilm recording medium disposed under the thin window portion.

22. An electron beam COM printer system according to claim 16, whereinan extremely fine elongated slit window portion is provided having awidth on the order of the diameter of the electron beam and means areprovided for repetitively scanning the electron beam in the direction ofthe longitudinal axis of the elongated window portion together withmeans for blanking the beam of electrons at appropriate points along thepath of travel thereof whereby partial character recording is achievedduring each scan of the electron beam. and the transport means moves themicrofilm recording medium transverse to the longitudinal dimension ofthe elongated fine slit window portion intermediate each scan wherebyduring successive scans of the electron beam raster recording of linesof complete alphanumeric characters is achieved by the accumulation ofpartial character recordings accomplished during each respective scan ofthe electronic beam.

23. An electron beam COM printer system according to claim 22 whereinthe thin window portion is formed by chemical reaction with the bulksupporting member and the differentially etched bulk supporting member Iand thin window portion of the electron beam recording apparatus arefrom the class of materials consisting essentially of silicon-silicondioxide (Si-SiOfl; aluminum-aluminum oxide (Al-A1 0 tantalum-tantalumoxide (Ta-TaO); titanium-titanium oxide (Ti-TiO); silicon-siliconnitride (Si-SiN); and silicon-silicon carbide (Si-SiC);silicon-aluminium oxide (Si-M 0 24. An electron beam COM printer systemaccording to claim 22 wherein the differentially etched bulk supportingmember comprising a part of the electron beam recording apparatus issilicon and the thin window portion thereof is comprised by a thin layerof silicon dioxide previously formed to a desired thickness on thesurface of the bulk supporting silicon member by chemical reaction priorto etching the window therein and the elongated thin slit window portionhas a longitudinal dimension on the order of the length of a line ofrecorded characters and a width on the order of 5 microns with thethickness of the window portion being on the order of SOD-2,000 angstromunits.

25. An electron beam COM printer system according to claim 24, whereinthe means for blanking the beam of electrons at appropriate pointsduring each individual scan thereof comprises on-off blanking signalssupplied to the control grid of the electron beam recording apparatusfrom the character generator circuit means.

26. An electron beam COM printer system according to claim 24, whereinthe means for blanking the beam of electrons at appropriate pointsduring each individual scan thereof comprises deflecting means fordeflecting the electron beam transversely to the longitudinal axis ofthe elongated thin slit window portion so that the sides of thesupporting bulk member intercept and blank the beam at points where beamblanking is desired.

27. An electron beam COM printer system including in combination anelectron beam recording apparatus comprising an evacuated housing havinga source of electrons disposed therein and controlled by a control grid,means for directing the electrons in a beam toward one end of thehousing, a Lenard window secured to the housing against which theelectrons are directed, said Lenard window being fabricated from adifferentially etched bulk supporting member secured to the wall of theevacuated housing and having an extremely thin window portion in theform of an elongated thin slit through which the electron beam isdirected to permit egress of the electron beam out of the evacuatedhousing, said elongated slit thin window portion consisting of amaterial formed on but different than the bulk supporting member and notsusceptible to the etchant employed to form the window in the bulksupporting member, deflecting means for deflecting the electron beamalong the longitudinal axis of the elongated thin slit window portion,an electron sensitive microfilm tape recording medium, tape transportmeans for disposing the microfilm tape recording medium immediatelyadjacent the elongated slit window portion of the electron beamrecording apparatus and for transporting the tape past the windowportion in a direction transverse to the longitudinal axis of theelongated thin slit window portion, developing means for developingelectron images recorded on the microfilm tape recording medium, printercontrol circuit means coupled to the deflecting means for said electronbeam recording apparatus, to said tape transport means and to saiddeveloping means for controlling the operation thereof, and charactergenerator circuit means controlled by the printer control circuit meansand coupled to the control grid for the electron source of the electronbeam recording apparatus for controlling operation of the electron beamrecording apparatus in conjunction with the printer control circuitmeans whereby the electron beam is caused repetitively to scan along thelongitudinal axis of the elongated thin slit window portion and isblanked at appropriate points in accordance with characters to berecorded, said printer control circuit means and said charactergenerator circuit means being controlled from the output of anelectronic computer system with which the COM printer is used as aprint-out device.

28. An electron beam COM printer system according to claim 27, whereinthe differentially etched bulk supporting member and thin window portionare from the class of materials consisting essentially ofsilicon-silicon dioxide (Si-SiO aluminum-aluminum oxide (Al-Al,0;,);tantalum-tan talum oxide (TaTaO); and titanium-titanium oxide (Ti-TiO);siliconsilicon nitride (Si-SiN); silicon-silicon carbide (Si-SiC); andsilicon-aluminium oxide (Si-M 29. An electron beam COM printer systemaccording to claim 27, wherein an extremely fine slit window portion isprovided having a width on the order of the diameter of the electronbeam whereby partial character recording is achieved during eachscanning of the electron beam across the longitudinal direction of thewindow portion accompanied with appropriate beam blanking at selectedpoints along the path of travel thereof to provide character spacing andformatting, and the transport means moves the microfilm recording mediumtransverse to the longitudinal dimension of the elongated thin slitwindow portion intermediate each scan whereby during successive scans ofthe electron beam raster recording of lines of complete alphanumericcharacters is achieved by the accumulation of partial characterrecordings accomplished during each respective scan of the electronbeam.

30. An electron beam COM printer system according to claim 27, furtherincluding buffer memory means intercoupled with the printer controlcircuit means and the character generator means for receiving apredetermined number of lines of data to be printed from a computersystem central processing unit plus control instructions for directingoperations of the printer control circuit means. said buffer memorymeans serving to store temporarily the predetermined number of lines ofdata plus control instructions while it is being printed out by the COMprinter device thereby freeing the computer system central processingunit for further operations during printing of the stored lines of data.

31. An electron beam COM printer system according to claim 30, whereineach character recorded on the microfilm tape recording medium iscomprised of a matrix of horizontal coextending and verticaltransversely placed dots measured with respect to the longitudinal axisof the elongated thin slit window and with the equivalent of apredetermined number of dot spacings between characters in each line andbetween each line of characters, the placement of a dot in the formationof a character in a line of characters and the spacing thereof withrespect to other dots comprising the character and line of charactersbeing controlled by appropriate manipulation of the beam deflectionmeans and beam blanking means of the electron beam recording apparatus.

32. An electron beam COM printer system according to claim 31, whereinthe printer control circuit means comprises dot clock pulse and controlcircuit means coupled to and responsive to the buffer memory means forgenerating the basic dot clock pulse signal, horizontal dotposition-in-a-character counter means responsive to the dot clock pulseand control circuit means, horizontal characters-in-a-line counter meansresponsive to the horizontal dot position-in-a-character counter meansand coupled to and controlling a ramp generator means for driving thedeflection means for deflecting the electron beam horizontally along thelongitudinal axis of the elongated thin slit window portion. means forcoupling the output from said characters-ina-line counter means back tothe input of the dot clock pulse and control circuit means forinhibiting operation of said dot clock pulse and control circuit meansduring the retrace portion of the beam deflection means, verticalline-in-a-page counter means coupled to the output from saidcharacters-in-a-line counter means and controllingsaid tape transportand developing means, vertical-dot-position-in-a-character counter meansresponsive to the output from the characters-in-a-line counter means,said character generator means comprising a read only memory matrixresponsive to the buffer memory means and the output of thevertical-dotposition-in-a-character counter means and digitalmultiplexing circuit means supplied with said dot clock pulses andcontrolled by read only memory matrix for controlling the grid drivingamplifier supplying the control grid of the electron beam recordingapparatus for intensifying the electron beam at points where dots are tobe recorded.

33. An electron beam COM printer system according to claim 32, whereinan extremely fine elongated slit window portion is provided having awidth on the order of the diameter of the electron beam whereby partialcharacter recording is achieved during each individual scan andrecording of a complete character is accomplished by a series ofsuccessive scans of the electron beam across the longitudinal axis ofthe elongated thin slit window portion accompanied with appropriateintensification of the electron beam at selected points as determined bythe read only memory along the path of travel of the electron beam toprovide dot spacing and fonnatting of the characters being printed.

34. An electron beam COM printer system according to claim 33, whereinthe differentially etched bulk supporting member is silicon and the thinwindow portion is comprised by a thin layer of silicon dioxidepreviously formed to a desired thickness on the surface of the bulksupporting silicon member by chemical reaction prior to etching thewindow therein and the elongated thin slit window portion has alongitudinal dimen-

2. thin electron beam apparatus according to claim 1, wherein the thinkwindow portion is formed by chemical reaction with the bulk supportingmember and the differentially etched bulk supporting member and thinwindow portion are from the class of materials consisting essentially ofsilicon-silicon dioxide (Si-SiO2); aluminum-aluminum oxide (Al-Al2O3);tantalum-tantalum oxide (Ta-TaO); titanium-titanium oxide (Ti-TiO);silicon-silicon nitride (Si-SiN); silicon-silicon carbide (Si-SiC)silicon-aluminum oxide (Si-Al2O3).
 3. An electron beam apparatusaccording to claim 1, wherein the differentially etched bulk supportingmember has a thin conductive layer formed over at least a part of thesurface of bulk supporting member exposed to the electron beam andextending over at least part of the thin window portion whereby build-upof a substantial charge on the window can be minimized.
 4. An electronbeam apparatus according to claim 1, wherein the electron beam apparatusis of the type including deflecting means for deflecting the electronbeam along at least one axis of movement and said window portioncomprises an elongated thin slit having its long axis extending in thedirection of deflection of the electron beam. 5 An electron beamapparatus according to claim 1, wherein said window portion comprises anelongated thin slit having a width which is more narrow than the largestdimension of the cross section of an elongated electron beam produced bythe electron beam apparatus.
 6. An electron beam apparatus to claim 1,wherein the differentially etched bulk supporting meMber is silicon andthe thin window portion is comprised by a thin layer of silicon dioxidepreviously formed to a desired thickness on the surface of the bulksupporting silicon member by controlled chemical reaction prior toetching the window therein and wherein the thin slit window portion as awidth on the order of 5-75 microns and a thickness on the order of500-2,000 angstrom units.
 7. An electron beam apparatus according toclaim 4, wherein the electron beam apparatus further includes additionalmicro deflecting means for deflecting the electron beam along twotransverse axes of movement with respect to a character wide thin slitwindow portion for writing a line of alphanumeric characters, and beamblanking means for blanking the electron beam at appropriate pointsalong the line of characters to provide for separation and formatting ofthe written characters.
 8. An electron beam apparatus according to claim4, wherein an array of characters masks having openings there in formingalphanumeric characters are arranged along the longitudinal dimension ofthe elongated thin slit window portion and the deflecting means servesto deflect the electron beam to a selected character on one of thecharacter masks, and the electron beam apparatus further includes microdeflection means disposed intermediate the array of character masks andthe first mentioned deflecting means for focusing and deflecting adesired alphanumeric character-shaped electron beam produced by passageof the electron beam through a selected character opening on one of thecharacter masks to cause the same to be directed through the thin windowportion and a desired point along its length.
 9. An electron beamapparatus according to claim 4, wherein an extremely fine slit windowportion is provided having a width on the order of the diameter of theelectron beam whereby partial character recording can be achieved duringeach scan of the electron beam across the longitudinal direction of thewindow portion accompanied with appropriate beam blanking at selectedpoints along the path of travel thereof to provide character spacing andformatting and repetitive scans of the electron beam are required forcomplete character recording.
 10. An electron beam apparatus accordingto claim 9, wherein the differentially etched bulk supporting member issilicon and the thin window portion is comprised by a thin layer ofsilicon dioxide previously formed on the surface of the bulk supportingsilicon member prior to etching the window therein and the elongatedthin slit window portion has a longitudinal dimension on the order ofthe length of a line of recorded characters and a thin width portion onthe order of 5 microns with the thickness of the window portion being onthe order of 500-2,000 angstrom units.
 11. An electron beam apparatusaccording to claim 9, further including means for blanking the beam ofelectrons at appropriate points along the path of travel thereof duringthe scanning of the beam in the longitudinal direction of the thin slitwindow portion.
 12. An electron beam apparatus according to claim 11,wherein said electron beam blanking means comprises means for producingsuitable on-off blanking signals supplied to the control grid of theelectron beam apparatus.
 13. An electron beam apparatus according toclaim 11, wherein said electron beam blanking means comprises deflectingmeans for deflecting the electron beam transversely to the longitudinalaxis of the elongated thin slit window portion so that the sides of thesupporting bulk member intercept and blank the beam at points where beamblanking is desired.
 14. An electron beam COM printer system includingan electron beam apparatus of the type set forth in claim 1, an electronsensitive microfilm recording medium, transport means for supporting themicrofilm recording medium immediately adjacent the thin window portionof the electron beam recording apparatus for recording data thereon,printer cOntrol circuit means coupled to said electron beam writingapparatus and the transport means for controlling the operation thereof,and character generator circuit means controlled by the printer controlcircuit means and coupled to the electron beam writing apparatus forcontrolling the operation thereof in conjunction with the printercontrol circuit means, said printer control circuit means and saidcharacter generator circuit means being controlled from the output of acomputer system with which the COM printer is used as a print-outdevice.
 15. An electron beam COM printer system according to claim 14,further including buffer memory means intercoupled with the printercontrol circuit means and the character generator means for receiving apredetermined number of lines of data to be printed from a computersystem central processing unit plus control data for directing operationof the printer control circuit means, said buffer memory means servingto store temporarily the predetermined number of lines of data whileeach line of data is being printed out by the COM printer therebyfreeing the computer system central processing unit for furtheroperations during printing of the stored lines of data.
 16. An electronbeam COM printer system according to claim 15, wherein the electron beamrecording apparatus is of the type including deflecting means fordeflecting the electron beam along at least one axis of movement and thewindow portion comprises an elongated thin slit having its long axisextending in the direction of deflection of the electron beam, saidtransport means operates to move the microfilm recording medium in adirection transverse to the longitudinal axis of the elongated thin slitwindow whereby successive lines of data can be recorded raster fashion,said printer control circuit means is coupled to and controls operationof the deflecting means to cause tracing of the electron beam along thelongitudinal dimension of the elongated thin slit window portion, andthe character generator circuit means controls beam blanking andcharacter formatting.
 17. An electron beam COM printer system accordingto claim 16, wherein the differentially etched bulk supporting member issilicon and the thin window portion is comprised by a thin layer ofsilicon dioxide previously formed on the surface of the bulk supportingsilicon member by chemical reaction prior to etching the window thereinand wherein the thin slit window portion has a length on the order ofone line of recorded alphanumeric characters on microfilm, a width onthe order of 75 microns and a thickness on the order of 1,000-5,000angstrom units.
 18. An electron beam COM printer system according toclaim 17, further including means enclosing the Lenard window portion ofthe electron beam apparatus and the microfilm disposed immediatelyadjacent the Lenard window portion in an enclosed space maintained at areduced pressure relative to the surrounding ambient atmosphere.
 19. Anelectron beam COM printer system according to claim 16, wherein saidwindow portion comprises an elongated thin slit having its longestdimension approximating the length of a line of microfilm recordedalphanumeric characters and having the thin dimension thereofapproximating the height of an individual alphanumeric characterrecorded on microfilm, and wherein the electron beam recording apparatusfurther includes additional micro deflecting means for deflecting theelectron beam along two transverse axes of movement with respect to thecharacter wide elongated thin slit window portion for writing a line ofalphanumeric characters, and beam blanking means for blanking theelectron beam at appropriate points along the line of characters toprovide for separation and formatting of the written line of characters,said character generator circuit means controlling operation of bothsaid additional micro deflecting means and said beam blanking means. 20.An electron beam COM printer sysTem according to claim 19, wherein thedifferentially etched bulk supporting member is silicon and the thinwindow portion is comprised by a thin layer of silicon dioxidepreviously formed on the surface of the bulk supporting member bychemical reaction prior to etching the window therein and wherein thethin slit window portion has a width on the order of 75 microns and athickness on the order of 1,000-5,000 angstom units.
 21. An electronbeam COM printer system according to claim 16, wherein an array ofcharacter masks having openings therein forming alphanumeric charactersare arranged along the longitudinal axis of the elongated thin slitwindow portion and the deflecting means serves to deflect the electronbeam to a selected character on one of the character masks, and saidelectron beam recording apparatus further including micro deflectionmeans disposed intermediate the array of character masks and the firstmentioned deflecting means for focusing and deflecting a desiredalphanumeric character-shaped electron beam produced by passage of theelectron beam through a selected character opening on one of thecharacter masks to cause the same to be directed through the thin windowportion at a desired point along its length and thereby record anelectron image of the selected character at a desired point on themicrofilm recording medium disposed under the thin window portion. 22.An electron beam COM printer system according to claim 16, wherein anextremely fine elongated slit window portion is provided having a widthon the order of the diameter of the electron beam and means are providedfor repetitively scanning the electron beam in the direction of thelongitudinal axis of the elongated window portion together with meansfor blanking the beam of electrons at appropriate points along the pathof travel thereof whereby partial character recording is achieved duringeach scan of the electron beam, and the transport means moves themicrofilm recording medium transverse to the longitudinal dimension ofthe elongated fine slit window portion intermediate each scan wherebyduring successive scans of the electron beam raster recording of linesof complete alphanumeric characters is achieved by the accumulation ofpartial character recordings accomplished during each respective scan ofthe electronic beam.
 23. An electron beam COM printer system accordingto claim 22 wherein the thin window portion is formed by chemicalreaction with the bulk supporting member and the differentially etchedbulk supporting member and thin window portion of the electron beamrecording apparatus are from the class of materials consistingessentially of silicon-silicon dioxide (Si-SiO2); aluminum-aluminumoxide (Al-Al2O3); tantalum-tantalum oxide (Ta-TaO); titanium-titaniumoxide (Ti-TiO); silicon-silicon nitride (Si-SiN); and silicon-siliconcarbide (Si-SiC); silicon-aluminium oxide (Si-Al2O3).
 24. An electronbeam COM printer system according to claim 22 wherein the differentiallyetched bulk supporting member comprising a part of the electron beamrecording apparatus is silicon and the thin window portion thereof iscomprised by a thin layer of silicon dioxide previously formed to adesired thickness on the surface of the bulk supporting silicon memberby chemical reaction prior to etching the window therein and theelongated thin slit window portion has a longitudinal dimension on theorder of the length of a line of recorded characters and a width on theorder of 5 microns with the thickness of the window portion being on theorder of 500-2,000 angstrom units.
 25. An electron beam COM printersystem according to claim 24, wherein the means for blanking the beam ofelectrons at appropriate points during each individual scan thereofcomprises on-off blanking signals supplied to the control grid of theelectron beam recording apparatus from the characTer generator circuitmeans.
 26. An electron beam COM printer system according to claim 24,wherein the means for blanking the beam of electrons at appropriatepoints during each individual scan thereof comprises deflecting meansfor deflecting the electron beam transversely to the longitudinal axisof the elongated thin slit window portion so that the sides of thesupporting bulk member intercept and blank the beam at points where beamblanking is desired.
 27. An electron beam COM printer system includingin combination an electron beam recording apparatus comprising anevacuated housing having a source of electrons disposed therein andcontrolled by a control grid, means for directing the electrons in abeam toward one end of the housing, a Lenard window secured to thehousing against which the electrons are directed, said Lenard windowbeing fabricated from a differentially etched bulk supporting membersecured to the wall of the evacuated housing and having an extremelythin window portion in the form of an elongated thin slit through whichthe electron beam is directed to permit egress of the electron beam outof the evacuated housing, said elongated slit thin window portionconsisting of a material formed on but different than the bulksupporting member and not susceptible to the etchant employed to formthe window in the bulk supporting member, deflecting means fordeflecting the electron beam along the longitudinal axis of theelongated thin slit window portion, an electron sensitive microfilm taperecording medium, tape transport means for disposing the microfilm taperecording medium immediately adjacent the elongated slit window portionof the electron beam recording apparatus and for transporting the tapepast the window portion in a direction transverse to the longitudinalaxis of the elongated thin slit window portion, developing means fordeveloping electron images recorded on the microfilm tape recordingmedium, printer control circuit means coupled to the deflecting meansfor said electron beam recording apparatus, to said tape transport meansand to said developing means for controlling the operation thereof, andcharacter generator circuit means controlled by the printer controlcircuit means and coupled to the control grid for the electron source ofthe electron beam recording apparatus for controlling operation of theelectron beam recording apparatus in conjunction with the printercontrol circuit means whereby the electron beam is caused repetitivelyto scan along the longitudinal axis of the elongated thin slit windowportion and is blanked at appropriate points in accordance withcharacters to be recorded, said printer control circuit means and saidcharacter generator circuit means being controlled from the output of anelectronic computer system with which the COM printer is used as aprint-out device.
 28. An electron beam COM printer system according toclaim 27, wherein the differentially etched bulk supporting member andthin window portion are from the class of materials consistingessentially of silicon-silicon dioxide (Si-SiO2); aluminum-aluminumoxide (Al-Al2O3); tantalum-tantalum oxide (Ta-TaO); andtitanium-titanium oxide (Ti-TiO); silicon-silicon nitride (Si-SiN);silicon-silicon carbide (Si-SiC); and silicon-aluminium oxide(Si-Al2O3).
 29. An electron beam COM printer system according to claim27, wherein an extremely fine slit window portion is provided having awidth on the order of the diameter of the electron beam whereby partialcharacter recording is achieved during each scanning of the electronbeam across the longitudinal direction of the window portion accompaniedwith appropriate beam blanking at selected points along the path oftravel thereof to provide character spacing and formatting, and thetransport means moves the microfilm recording medium transverse to thelongitudinal dimension of the elongated thin slit window portionintermediate each scan whereby during successive scans of the electronbeam raster recording of lines of complete alphanumeric characters isachieved by the accumulation of partial character recordingsaccomplished during each respective scan of the electron beam.
 30. Anelectron beam COM printer system according to claim 27, furtherincluding buffer memory means intercoupled with the printer controlcircuit means and the character generator means for receiving apredetermined number of lines of data to be printed from a computersystem central processing unit plus control instructions for directingoperations of the printer control circuit means, said buffer memorymeans serving to store temporarily the predetermined number of lines ofdata plus control instructions while it is being printed out by the COMprinter device thereby freeing the computer system central processingunit for further operations during printing of the stored lines of data.31. An electron beam COM printer system according to claim 30, whereineach character recorded on the microfilm tape recording medium iscomprised of a matrix of horizontal coextending and verticaltransversely placed dots measured with respect to the longitudinal axisof the elongated thin slit window and with the equivalent of apredetermined number of dot spacings between characters in each line andbetween each line of characters, the placement of a dot in the formationof a character in a line of characters and the spacing thereof withrespect to other dots comprising the character and line of charactersbeing controlled by appropriate manipulation of the beam deflectionmeans and beam blanking means of the electron beam recording apparatus.32. An electron beam COM printer system according to claim 31, whereinthe printer control circuit means comprises dot clock pulse and controlcircuit means coupled to and responsive to the buffer memory means forgenerating the basic dot clock pulse signal, horizontal dotposition-in-a-character counter means responsive to the dot clock pulseand control circuit means, horizontal characters-in-a-line counter meansresponsive to the horizontal dot position-in-a-character counter meansand coupled to and controlling a ramp generator means for driving thedeflection means for deflecting the electron beam horizontally along thelongitudinal axis of the elongated thin slit window portion, means forcoupling the output from said characters-in-a-line counter means back tothe input of the dot clock pulse and control circuit means forinhibiting operation of said dot clock pulse and control circuit meansduring the retrace portion of the beam deflection means, verticalline-in-a-page counter means coupled to the output from saidcharacters-in-a-line counter means and controlling said tape transportand developing means, vertical-dot-position-in-a-character counter meansresponsive to the output from the characters-in-a-line counter means,said character generator means comprising a read only memory matrixresponsive to the buffer memory means and the output of thevertical-dot-position-in-a-character counter means and digitalmultiplexing circuit means supplied with said dot clock pulses andcontrolled by read only memory matrix for controlling the grid drivingamplifier supplying the control grid of the electron beam recordingapparatus for intensifying the electron beam at points where dots are tobe recorded.
 33. An electron beam COM printer system according to claim32, wherein an extremely fine elongated slit window portion is providedhaving a width on the order of the diameter of the electron beam wherebypartial character recording is achieved during each individual scan andrecording of a complete character is accomplished by a series ofsuccessive scans of the electron beam across the longitudinal axis ofthe elongated thin slit window portion accompanied with appropriateintensification of the electron beam at selected points as determined bythe read onlY memory along the path of travel of the electron beam toprovide dot spacing and formatting of the characters being printed. 34.An electron beam COM printer system according to claim 33, wherein thedifferentially etched bulk supporting member is silicon and the thinwindow portion is comprised by a thin layer of silicon dioxidepreviously formed to a desired thickness on the surface of the bulksupporting silicon member by chemical reaction prior to etching thewindow therein and the elongated thin slit window portion has alongitudinal dimension corresponding to the length of a line of 132recorded alphanumeric characters plus appropriate spacing betweencharacters and a width on the order of 5 microns with the thickness ofthe window portion being on the order of 500-2,000 angstrom units. 35.An electron beam COM printer system including in combination an electronbeam recording apparatus comprising an evacuated housing having a sourceof electrons disposed therein and controlled by a control grid, meansfor directing the electrons in a beam toward one end of the housing, atarget window secured to the housing against which the electrons aredirected, said target window being capable of emanating radiationexterior of said housing through an extremely thin window portion in theform of an elongated thin slit through which radiation is directed topermit egress out of the evacuated housing, said target windowscomprising a bulk supporting portion having a window etched therein andsecured to said housing and said thin window portion being formed from amaterial different from the bulk supporting portion and not susceptibleto the etchant employed to form the window in the bulk supportingportion, deflecting means for deflecting the electron beam along thelongitudinal axis of the elongated thin slit target window, a microfilmtape recording medium, tape transport means for disposing the microfilmtape recording medium immediately adjacent the elongated slit targetwindow of the electron beam recording apparatus and for transporting thetape past the window in a direction transverse to the longitudinal axisof the elongated thin slit target window developing means for developingimages recorded on the microfilm tape recording medium, printer controlcircuit means coupled to the deflecting means for said electron beamrecording apparatus, to said tape transport means and to said developingmeans for controlling the operation thereof, and character generatorcircuit means controlled by the printer control circuit means andcoupled to the control grid for the electron source of the electron beamrecording appartus for controlling operation of the electron beamrecording apparatus in conjunction with the printer control circuitmeans whereby the electron beam is caused repetitively to scan along thelongitudinal axis of the elongated thin slit target window and isblanked at appropriate points in accordance with characters to berecorded, said printer control circuit means and said charactergenerator circuit means being controlled from the output of anelectronic computer system with which the COM printer is used as aprint-out device.
 36. An electron beam COM printer system according toclaim 35, further including buffer memory means intercoupled with theprinter control circuit means and the character generator means forreceiving a predetermined number of lines of data to be printed from acomputer system central processing unit plus control instructions fordirecting operation of the printer control circuit means, said buffermemory means serving to store temporarily the predetermined number oflines of data while it is being printed out by the COM printer devicethereby freeing the computer system central processing unit for furtheroperations during printing of the stored lines of data.
 37. An electronbeam COM printer system according to claim 36, wherein each characterrecorded on the microfilm tape recording medium is comprised Of a matrixof horizontal dots coextensive with the longitudinal axis of theelongated thin slit window and vertical dots disposed transverse to thelongitudinal axis of the elongated thin slit window with the equivalentof a predetermined number of dot spacings between characters and eachline of characters, the placement of a dot in the formation of acharacter in a line of characters and the spacing thereof with respectto other dots comprising the character and line of characters beingcontrolled by appropriate manipulation of the beam deflection means andbeam blanking means for the electron beam recording apparatus.
 38. Anelectron beam COM printer system according to claim 37, wherein theprinter control circuit means comprises dot clock pulse and controlcircuit means coupled to and responsive to the buffer memory means forgenerating the basic dot clock pulse signal, horizontal dotposition-in-a-character counter means responsive to the dot clock pulseand control circuit means, horizontal characters-in-a-line counter meansresponsive to the horizontal dot position-in-a-character counter meansand coupled to and controlling a ramp generator means for driving thedeflection means for deflecting the electron beam horizontally along thelongitudinal axis of the elongated thin slit target window, means forcoupling the output from said characters-in-a-line counter means back tothe input of the dot clock pulse and control circuit means forinhibiting operation of said dot clock pulse and control circuit meansduring the retrace portion of the beam deflection means, verticalline-in-a-page counter means coupled to the output from saidcharacters-in-a-line counter means and controlling said tape transportand developing means, vertical dot-position-in-a-character counter meansresponsive to the output from the characters-in-a-line counter means,said character generator means comprising a read only memory matrixresponsive to the buffer memory means and the output of the vertical dotposition-in-a-character counter means, and digital multiplexing circuitmeans supplied with said dot clock pulses and controlled by said readonly memory matrix for controlling the grid driving amplifier supplyingthe control grid of the electron beam recording apparatus forintensifying the electron beam at points where dots are to be recorded.